The Hadza are hunter-gatherers: For a thorough discussion of everything Hadza, see: Frank Marlowe, The Hadza: Hunter-Gatherers of Tanzania (Univ. of California Press, 2010).
37 trillion cells: E. Bianconi et al. (2013). “An estimation of the number of cells in the human body.” Ann. Hum. Biol. 40 (6): 463–71, doi: 10.3109/03014460.2013.807878.
an ounce of the Sun: A 70-kg human burns approximately 2,800 kilocalories per day, or 40 kcal/kg per day. The Sun has a mass of 1.989×1030 and produces 7.942×1027 kcal per day, or a paltry 0.004 kcal/kg per day. See Vaclav Smil, Energies: An Illustrated Guide to the Biosphere and Civilization (MIT Press, 1999).
Nine-year-olds burn 2,000 calories: N. F. Butte (2000). “Fat intake of children in relation to energy requirements.” Am. J. Clin. Nutr. 72 (suppl): 1246S–52S.
most doctors don’t, either: R. Meerman and A. J. Brown (2014). “When somebody loses weight, where does the fat go?” BMJ 349: g7257.
U.S. federal government: Chris Cilliza, “Americans know literally nothing about the Constitution,” CNN, last modified September 13, 2017, https://www.cnn.com/2017/09/13/politics/poll-constitution/index.html.
dead by twenty-five: Author’s unpublished analyses, calculated from allometric regressions between body mass and age at maturity, maximum lifespan, and neonate size for placental mammals, using the AnAge database. R. Tacutu et al. (2018). “Human Ageing Genomic Resources: new and updated databases.” Nucl. Acids Res. 46 (D1): D1083–90. doi: 10.1093/nar/gkx1042.
compared to other mammals: E. L. Charnov and D. Berrigan (1993). “Why do female primates have such long lifespans and so few babies? or Life in the slow lane.” Evol. Anthro. 1 (6): 191–94.
killed early by a predator or other malefactor favor a slower pace of life: S. C. Stearns, M. Ackermann, M. Doebeli, and M. Kaiser (2000). “Experimental evolution of aging, growth, and reproduction in fruitflies.” PNAS 97 (7): 3309–13; S. K. Auer, C. A. Dick, N. B. Metcalfe, and D. N. Reznick (2018). “Metabolic rate evolves rapidly and in parallel with the pace of life history.” Nat. Commun. 9: 14.
stronger, pound for pound, than humans: M. C. O’Neill et al. (2017). “Chimpanzee super strength and human skeletal muscle evolution.” PNAS 114 (28): 7343–48; K. Bozek et al. (2014). “Exceptional evolutionary divergence of human muscle and brain metabolomes parallels human cognitive and physical uniqueness.” PLoS Biol. 12 (5): e1001871. doi: 10.1371/journal.pbio.1001871.
proponents of this hypothesis, like Brian McNab: Brian K. McNab (2008). “An analysis of the factors that influence the level and scaling of mammalian BMR.” Comp. Biochem. Phys. A—Mol. Integ. Phys. 151: 5–28.
faster pace of life presumably requires a faster metabolic engine: T. J. Case (1978). “On the evolution and adaptive significance of postnatal growth rates in the terrestrial vertebrates.” Quar. Rev. Biol. 53 (3): 243–82.
studies built upon these results, and a consensus developed: P. H. Harvey, M. D. Pagel, and J. A. Rees (1991). “Mammalian metabolism and life histories.” Am. Nat. 137 (4): 556–66.
Orangutans burned fewer calories each day than humans: H. Pontzer et al. (2010). “Metabolic adaptation for low energy throughput in orangutans.” PNAS 107 (32): 14048–52.
three-toed sloths and pandas: Y. Nie et al. (2015). “Exceptionally low daily energy expenditure in the bamboo-eating giant panda.” Science 349 (6244): 171–74.
everything we knew about orangutan ecology and biology: Serge A. Wich, S. Suci Utami Atmoko, Tatang Mitra Setia, and Carel P. van Schaik, Orangutans: Geographic Variation in Behavioral Ecology and Conservation (Oxford Univ. Press, 2008).
Primates burn only half as many calories: H. Pontzer et al. (2014). “Primate energy expenditure and life history.” PNAS 111 (4): 1433–37.
1995 paper by Leslie Aiello and Peter Wheeler: L. C. Aiello and P. Wheeler (1995). “The Expensive Tissue Hypothesis: the brain and the digestive system in human and primate evolution.” Curr. Anthropol. 36: 199–221.
“nature is forced to economise on the other side”: Charles Darwin, On the Origin of Species (John Murray, 1861), 147.
primates in Southeast Asia: Arthur Keith (1891). “Anatomical notes on Malay apes.” J. Straits Branch Roy. Asiatic Soc. 23: 77–94.
the first doubly labeled water study in a wild primate: K. A. Nagy and K. Milton (1979). “Energy metabolism and food consumption by howler monkeys.” Ecology 60: 475–80.
smaller brains than fruit-eating species: K. Milton (1993). “Diet and primate evolution.” Scientific American, August, 86–93.
arguing that the cost of bigger brains: K. Isler and C. P. van Schaik (2009). “The Expensive Brain: A framework for explaining evolutionary changes in brain size.” J. Hum. Evol. 57: 392–400.
had evolved distinct daily energy expenditures: H. Pontzer et al. (2016). “Metabolic acceleration and the evolution of human brain size and life history.” Nature 533: 390–92.
the combination of work done and heat gained: I’m simplifying slightly by lumping the formation energy of making molecules (which should also be included in an exhaustive accounting of energy) along with the mechanical work of moving things.
releases enough energy (730 kilocalories): J. Taylor and R. L. Hall (1947). “Determination of the heat of combustion of nitroglycerin and the thermochemical constants of nitrocellulose.” J. Phys. Chem. 51 (2): 593–611.
by one degree Celsius (1.8 degrees Fahrenheit): The energy needed to raise a milliliter of water 1 degree Celsius depends slightly on the starting temperature of the water. The modern definition of a calorie is the energy equivalent of 4.184 joules. One joule is defined as the energy needed to lift 1 kilogram of mass upward by 1 meter (against gravity). Joules are named after the English scientist James Prescott Joule, who figured out the relationship between mechanical work and heat energy in the 1800s.
capitalize “Calories” when referring to kilocalories: J. L. Hargrove. (2006). “History of the Calorie in Nutrition.” J. Nutr. 136: 2957–61.
to convert joules on their food labels to calories: There are actually 4.18 joules per calorie, but dividing by four will be accurate to about 5 percent, which is close enough for daily use. Also, be aware that kJ is kilojoules (1,000 joules) and MJ is mega joules (1,000,000 joules).
little machine that builds baby flies: I thank Dr. Kenneth Weiss, professor at Penn State, for blowing my mind with this perspective during my formative college years.
65-million-year history of relying on them: R. W. Sussman (1991). “Primate origins and the evolution of angiosperms.” Am. J. Primatol. 23 (4): 209–23.
80 percent of the starches and sugars that you eat: R. Holmes (1971). “Carbohydrate digestion and absorption.” J. Clin. Path. 24, Suppl. (Roy. Coll. Path.) (5): 10–13.
blood flow to our guts more than doubles: P. J. Matheson, M. A. Wilson, and R. N. Garrison (2000). “Regulation of intestinal blood flow.” Jour. Surg. Res. 93: 182–96.
low glycemic index foods might be better for you: The evidence from carefully done studies on glycemic index are mixed. M. J. Franz (2003). “The glycemic index: Not the most effective nutrition therapy intervention.” Diabetes Care 26: 2466–68.
compared to a piece of orange, which does: F. S. Atkinson, K. Foster-Powell, and J. C. Brand-Miller (2008). “International tables of glycemic index and glycemic load values: 2008.” Diabetes Care 31 (12): 2281–83.
With trillions of bacteria: R. Sender, S. Fuchs, and R. Milo (2016). “Revised estimates for the number of human and bacteria cells in the body.” PLoS Biol. 14 (8): e1002533.
the microbiome is like a four-pound superorganism: I. Rowland et al. (2018). “Gut microbiota functions: Metabolism of nutrients and other food components.” Eur. J. Nutr. 57 (1): 1–24.
Carbs are energy: Sugars are also used to make some structures in the body. For example, the D in DNA is deoxyribose, which is a sugar molecule built from dietary carbohydrate.
Bile is a green juice produced by your liver: “Secretion of Bile and the Role of Bile Acids in Digestion,” Colorado State University, accessed March 13, 2020, http://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.html.
Bile acids (also called bile salts): M. J. Monte, J. J. Marin, A. Antelo, and J. Vazquez-Tato (2009). “Bile acids: Chemistry, physiology, and pathophysiology.” World J. Gastroenterol. 15 (7): 804–16.
obesity is a major risk factor: S. L. Friedman, B. A. Neuschwander-Tetri, M. Rinella, and A. J. Sanyal (2018). “Mechanisms of NAFLD development and therapeutic strategies.” Nat. Med. 24 (7): 908–22.
a typical alkaline battery: Wikipedia, accessed March 13, 2020, https://en.wikipedia.org/wiki/Energy_density.
sequence of amino acids to make a protein: I’m massively simplifying here, skipping over several steps from DNA to RNA to amino acid sequence. For a nice primer, see “Essentials of Genetics,” Nature Education, https://www.nature.com/scitable/ebooks/essentials-of-genetics-8/contents/.
tissues and molecules break down over time: G. E. Shambaugh III (1977). “Urea biosynthesis I. The urea cycle and relationships to the citric acid cycle.” Am. J. Clin. Nutr. 30 (12): 2083–87.
providing around 15 percent of our calories each day: C. E. Berryman, H. R. Lieberman, V. L. Fulgoni III, and S. M. Pasiakos (2018). “Protein intake trends and conformity with the Dietary Reference Intakes in the United States: Analysis of the National Health and Nutrition Examination Survey, 2001–2014.” Am. J. Clin. Nutr. 108 (2): 405–13.
each molecule cycles from ADP to ATP and back: Lawrence Cole, Biology of Life Biochemistry, Physiology and Philosophy (Academic Press, 2016).
the story is essentially the same for fructose and galactose: J. M. Rippe and T. J. Angelopoulos (2013). “Sucrose, high-fructose corn syrup, and fructose, their metabolism and potential health effects: What do we really know?” Adv. Nutr. 4 (2): 236–45.
circular track called the Krebs cycle: Discovered by Hans A. Krebs and William A. Johnson in 1937, earning Krebs a Nobel Prize in medicine. Krebs and his student Kurt Henseleit discovered the urea cycle in 1932. Krebs was probably happy to have been known for energy production rather than pee production.
not the atoms themselves: If we converted the mass of those atoms to energy, we have to follow Einstein’s famous formula, E = mc2, and we’d need a nuclear reactor. A gram of glucose would yield 21 billion kilocalories, vaporizing everything in sight.
Dogs have evolved to prey on our emotions: Brian Hare and Vanessa Woods, The Genius of Dogs: How Dogs Are Smarter Than You Think (Dutton, 2013).
a new recipe for photosynthesis evolved: R. M. Soo et al. (2017). “On the origins of oxygenic photosynthesis and aerobic respiration in Cyanobacteria.” Science 355 (6332): 1436–40.
struck by lightning, which are 1 in 700,000: “Flash Facts About Lightning,” National Geographic, accessed March 13, 2020, https://news.nationalgeographic.com/news/2004/06/flash-facts-about-lightning/.
over a million bacteria in an ounce: K. Lührig et al. (2015). “Bacterial community analysis of drinking water biofilms in southern Sweden.” Microbes Environ. 30 (1): 99–107.
about 330 million cubic miles of water: “How Much Water Is There on Earth?” USGS, https://water.usgs.gov/edu/earthhowmuch.html
championed by the visionary evolutionary biologist Lynn Margulis: Lynn Margulis, Origin of Eukaryotic Cells (Yale University Press, 1970).
Phlogiston was thought to be the essential stuff: Wikipedia, accessed March 13, 2020, https://en.wikipedia.org/wiki/Phlogiston_theory.
the chemist Joseph Priestley: “Joseph Priestley and the Discovery of Oxygen,” American Chemical Society, International Historic Chemical Landmarks, accessed March 13, 2020, http://www.acs.org/content/acs/en/education/whatischemistry/landmarks/josephpriestleyoxygen.html.
They placed a guinea pig in a small metal container: Esther Inglis-Arkell, “The Guinea Pig That Proved We Have an Internal Combustion Engine,” Gizmodo, last modified June 23, 2013, https://io9.gizmodo.com/the-guinea-pig-that-proved-we-have-an-internal-combusti-534671441.
oxygen consumption and CO2 production as the main measure: See pioneering work by Max Rubner, such as Max Rubner (1883). “Uber den Einfluss der Korpergrosse auf Stoff- und Kraftwechsel.” Zeitschr. f. Biol. 19: 535–62.
The Compendium of Physical Activity: B. E. Ainsworth et al. (2011). “Compendium of Physical Activities: A second update of codes and MET values.” Medicine and Science in Sports and Exercise 43 (8): 1575–81.
a large meta-analysis by Jonas Rubenson and colleagues: Jonas Rubenson et al. (2007). “Reappraisal of the comparative cost of human locomotion using gait-specific allometric analyses.” J. Experi. Biol. 210: 3513–24.
Hadza data fell right in line with this much larger sample: H. Pontzer et al. (2012). “Hunter-gatherer energetics and human obesity.” PLoS One 7 (7): e40503.
Studies of elite swimmers by Paola Zamparo: P. Zamparo et al. (2005). “Energy cost of swimming of elite long-distance swimmers.” Eur. J. Appl. Physiol. 94 (5–6): 697–704.
riding a bicycle is much cheaper: P. E. di Prampero (2000). “Cycling on Earth, in space, on the Moon.” Eur. J. Appl. Physiol. 82 (5–6): 345–60.
the cost of ascent increases with body weight: Elaine E. Kozma (2020), Climbing Performance and Ecology in Humans, Chimpanzees, and Gorillas (PhD dissertation, City University of New York).
Walking at our most economical pace, about 2.5 mph: D. Abe, Y. Fukuoka, and M. Horiuchi (2015). “Economical speed and energetically optimal transition speed evaluated by gross and net oxygen cost of transport at different gradients.” PLoS One 10: e0138154.
close to the energetically optimal speed: H. J. Ralston (1958). “Energy–speed relation and optimal speed during level walking.” Int. Z. Angew. Physiol. Einschl. Arbeitphysiol. 17 (4): 277–83.
People in big, fast-paced cities: M. H. Bornstein and H. G. Bornstein (1976). “The pace of life.” Nature 259: 557–59.
the inherent mechanics of a walking gait: Andrew Biewener and Shelia Patek, Animal Locomotion, 2nd ed. (Oxford Univ. Press, 2018).
the effect is typically small, around 1 to 4 percent: M. I. Lambert and T. L. Burgess (2010). “Effects of training, muscle damage and fatigue on running economy.” Internat. SportMed J. 11(4): 363–79.
increases the calories burned by only 3 to 13 percent: C. J. Arellano and R. Kram (2014). “The metabolic cost of human running: Is swinging the arms worth it?” J. Exp. Biol. 217: 2456–61.
half of a Big Mac (270 kcal): “McDonald’s Nutrition Calculator,” McDonald’s, accessed March 13, 2020, https://www.mcdonalds.com/us/en-us/about-our-food/nutrition-calculator.html.
calories in a chocolate glazed donut (340 kcal): “Nutrition.” Dunkin’ Donuts, accessed March 13, 2020, https://www.dunkindonuts.com/en/food-drinks/donuts/donuts.
BMR (in kcal per day) increases with body weight: Condensed from C. J. Henry (2005). “Basal metabolic rate studies in humans: Measurement and development of new equations.” Publ. Health Nutr. 8: 1133–52.
about 85 kcal per day for a typical 150-pound adult with 30 percent body fat: For a review of organ costs see: ZiMian Wang et al. (2012). “Evaluation of specific metabolic rates of major organs and tissues: Comparison between nonobese and obese women.” Obesity 20 (1): 95–100.
the low, low cost of about 2 calories per beat: M. Horiuchi et al. (2017). “Measuring the energy of ventilation and circulation during human walking using induced hypoxia.” Scientific Reports 7 (1): 4938. doi: 10.1038/s41598-017-05068-8
converting lactate, glycerol (from fat), and amino acids (from proteins): J. E. Gerich, C. Meyer, H. J. Woerle, and M. Stumvoll (2001). “Renal gluconeogenesis: Its importance in human glucose homeostasis.” Diabetes Care 24 (2): 382–91.
Like every other animal with a distinct mouth and butt: Many animals, like starfish, have only one hole, which serves for both bringing nutrients in and getting waste out. See A. Hejnol and M. Q. Martindale (2008). “Acoel development indicates the independent evolution of the bilaterian mouth and anus.” Nature 456 (7220): 382–86. doi: 10.1038/nature07309.
A recent study in mice by Sarah Bahr, John Kirby, and colleagues: S. M. Bahr et al. (2015). “Risperidone-induced weight gain is mediated through shifts in the gut microbiome and suppression of energy expenditure.” EBioMedicine 2 (11): 1725–34. doi: 10.1016/j.ebiom.2015.10.018.
providing nutrients and cleaning up waste: M. Bélanger, I. Allaman, and P. J. Magistretti (2011). “Brain energy metabolism: Focus on astrocyte-neuron metabolic cooperation.” Cell Metabolism 14 (6): 724–38.
increased their metabolic rates by only around 4 kcal per hour: R. W. Backs and K. A. Seljos (1994). “Metabolic and cardiorespiratory measures of mental effort: The effects of level of difficulty in a working memory task.” Int. J. Psychophysiol. 16 (1): 57–68; N. Troubat, M.-A. Fargeas-Gluck, M. Tulppo, and B. Dugué (2009). “The stress of chess players as a model to study the effects of psychological stimuli on physiological responses: An example of substrate oxidation and heart rate variability in man.” Eur. J. Appl. Physiol. 105 (3): 343–49.
Work by Christopher Kuzawa and colleagues: C. W. Kuzawa et al. (2014). “Metabolic costs of human brain development.” Proc. Nat. Acad. Sciences 111 (36): 13010–15. doi: 10.1073/pnas.1323099111.
thermoneutral zone is roughly between 75°F and 93°F: B. R. M. Kingma, A. J. H. Frijns, L. Schellen, and W. D. V. Lichtenbelt (2014). “Beyond the classic thermoneutral zone: Including thermal comfort.” Temperature 1 (2): 142–49.
a couple of degrees colder than adults who aren’t: R. J. Brychta et al. (2019). “Quantification of the capacity for cold-induced thermogenesis in young men with and without obesity.” J. Clin. Endocrin. Metab. 104 (10): 4865–78. doi: 10.1210/jc.2019-00728.
in the Arctic tend to have about 10 percent higher BMRs: W. R. Leonard et al. (2002). “Climatic influences on basal metabolic rates among circumpolar populations.” Am. J. Hum. Biol. 14 (5): 609–20.
shivering can cause our resting metabolic rate to climb: F. Haman and D. P. Blondin (2017). “Shivering thermogenesis in humans: Origin, contribution and metabolic requirement.” Temperature 4 (3): 217–26. doi: 10.1080/23328940.2017.1328999.
acute infections kill four out of ten children: M. Gurven and H. Kaplan (2007). “Longevity among hunter-gatherers: A cross-cultural examination.” Pop. and Devel. Rev. 33 (2): 321–65.
college men who reported to a student health clinic found their BMRs: M. P. Muehlenbein, J. L. Hirschtick, J. Z. Bonner, and A. M. Swartz (2010). “Toward quantifying the usage costs of human immunity: Altered metabolic rates and hormone levels during acute immune activation in men.” Am. J. Hum. Biol. 22: 546–56.
populations without the antiseptic advantages of modernization: M. D. Gurven et al. (2016). “High resting metabolic rate among Amazonian forager-horticulturalists experiencing high pathogen burden.” Am. J. Physical Anth. 161 (3): 414–25. doi: 10.1002/ajpa.23040.
Shuar kids five to twelve years old have BMRs that are about 200 kcal: S. S. Urlacher et al. (2019). “Constraint and trade-offs regulate energy expenditure during childhood.” Science Advances 5 (12): eaax1065. doi: 10.1126/sciadv.aax1065.
The cost of growth, then, is about 2,200 kcal per pound: J. C. Waterlow (1981). “The energy cost of growth. Joint FAO/WHO/UNU Expert Consultation on Energy and Protein Requirements.” Rome, accessed March 14, 2020, http://www.fao.org/3/M2885E/M2885E00.htm.
total cost of a healthy nine-month pregnancy is about 80,000 kcal: N. F. Butte and J. C. King (2005). “Energy requirements during pregnancy and lactation.” Publ. Health Nutr. 8: 1010–27.
directly tied to changes in the way these animals grow and reproduce: T. J. Case (1978). “On the evolution and adaptive significance of postnatal growth rates in the terrestrial vertebrates.” Quar. Rev. Biol. 53 (3): 243–82.
burning ten times more calories per day than their reptilian ancestors: K. A. Nagy, I. A. Girard, and T. K. Brown (1999). “Energetics of free-ranging mammals, reptiles, and birds.” Ann. Rev. Nutr. 19: 247–77.
Mammals grow five times faster than reptiles: Author’s unpublished analyses, calculated from allometric regressions between adult body mass and growth rate (g/yr) and reproductive output (g/yr), using the AnAge database. R. Tacutu et al. (2018). “Human Ageing Genomic Resources: New and updated databases.” Nucleic Acids Research 46 (D1): D1083–90.
Kleiber’s law of metabolism, named for the pioneering Swiss nutritionist: Max Kleiber, The Fire of Life: An Introduction to Animal Energetics (Wiley, 1961). Samuel Brody and Francis Benedict also contributed to this discovery.
in the neighborhood of Kleiber’s 0.75, ranging from 0.45 to 0.82: Author’s unpublished analyses, calculated from allometric regressions between adult body mass and growth rate (g/yr) and reproductive output (g/yr), using the AnAge database. R. Tacutu et al. (2018). “Human Ageing Genomic Resources: New and updated databases.” Nucleic Acids Research 46 (D1): D1083–90.
On Longevity and the Shortness of Life in 350 b.c.: Aristotle, On Longevity and Shortness of Life. Written 350 B.C.E. Translated by G. R. T. Ross, accessed March 16, 2020, http://classics.mit.edu/Aristotle/longev_short.html.
Rubner observed that the total energy expended per gram: Max Rubner, Das Problem det Lebensdaur und seiner beziehunger zum Wachstum und Ernarnhung (Oldenberg, 1908).
the American biologist Raymond Pearl: Raymond Pearl, The Biology of Death (J. B. Lippincott, 1922).
the free radical theory of aging: Denham Harman (1956). “Aging: A theory based on free radical and radiation chemistry.” J. Gerontol. 11 (3): 298–300.
don’t always show the expected effects on life span: Some studies find positive effects of antioxidant intake on mortality risk (e.g., L.-G. Zhao et al. [2017]. “Dietary antioxidant vitamins intake and mortality: A report from two cohort studies of Chinese adults in Shanghai.” J. Epidem. 27 [3]: 89–97), while others find no effect at all (e.g., U. Stepaniak et al. [2016]. “Antioxidant vitamin intake and mortality in three Central and Eastern European urban populations: The HAPIEE study.” Eur. J. Nutr. 55 [2]: 547–60).
researchers lamenting whether such links exist at all: For a skeptical view, see J. R. Speakman (2005). “Body size, energy metabolism, and lifespan.” J. Exp. Biol. 208: 1717–30.
reducing how much they’re allowed to eat leads to longer life spans: J. R. Speakman and S. E. Mitchell (2011). “Caloric restriction.” Mol. Aspects Med. 32: 159–221.
Greenland sharks can live four hundred years: J. Nielsen et al. (2016). “Eye lens radiocarbon reveals centuries of longevity in the Greenland shark (Somniosus microcephalus).” Science 353 (6300): 702–04.
heart rates (beats per minute) match the cellular metabolic rates: C. R. White and M. R. Kearney (2014). “Metabolic scaling in animals: Methods, empirical results, and theoretical explanations.” Compr. Physiol. 4 (1): 231–56. doi: 10.1002/cphy.c110049.
Frank Benedict and his colleague J. Arthur Harris had been amassing: J. A. Harris and F. G. Benedict (1918). “A biometric study of human basal metabolism.” PNAS 4 (12): 370–73. doi: 10.1073/pnas.4.12.370.
PARs are essentially the same as MET values: MET values are always 1 kcal per kg per hour, which is the average person’s BMR. PAR values are tailored to each individual’s BMR or estimated BMR.
still used by the World Health Organization: FAO Food and Nutrition Technical Report Series 1, FAO/WHO/UNU (2001). “Human energy requirements.” http://www.fao.org/docrep/007/y5686e/y5686e00.htm#Contents.
adults underreported actual food intake by 29 percent on average: L. Orcholski et al. (2015). “Under-reporting of dietary energy intake in five populations of the African diaspora.” Brit. J. Nutri. 113 (3): 464–72. doi: 10.1017/S000711451400405X.
you thought that the typical American eats a 2,000-kilocalorie diet: Marion Nestle and Malden Nesheim, Why Calories Count: From Science to Politics (Univ. of California Press, 2013).
Nathan Lifson, a physiologist at the University of Minnesota: A. Prentice (1987). “Human energy on tap.” New Scientist, November: 40–44.
oxygen atoms in the body water pool have an alternative: N. Lifson, G. B. Gordon, M. B. Visscher, and A. O. Nier (1949). “The fate of utilized molecular oxygen and the source of the oxygen of respiratory carbon dioxide, studied with the aid of heavy oxygen.” J. Biol. Chem. 180 (2): 803–11.
Lifson used those isotopes to track the flow oxygen and hydrogen: N. Lifson, G. B. Gordon, R. McClintock (1955). “Measurement of total carbon dioxide production by means of D218O.” J. Appl. Physiol. 7: 704–10.
isotope needed for a 150-pound human would cost more than $250,000: J. R. Speakman (1998). “The history and theory of the doubly labeled water technique.” Am. J. Clin. Nutr. 68 (suppl): 932S–38S.
the first doubly labeled water study in humans in 1982: D. A. Schoeller and E. van Santen (1982). “Measurement of energy expenditure in humans by doubly labeled water.” J. Appl. Physiol. 53: 955–59.
hundreds of doubly labeled water measurements of men, women, and children: L. Dugas et al. (2011). “Energy expenditure in adults living in developing compared with industrialized countries: A meta-analysis of doubly labeled water studies.” Am. J. Clin. Nutr. 93: 427–441; N. F. Butte (2000). “Fat intake of children in relation to energy requirements.” Am. J. Clin. Nutr. 72 (5 Suppl): 1246S–52S; H. Pontzer et al. (2012). “Hunter-gatherer energetics and human obesity.” PLoS One 7 (7): e40503.
Georgians reported two new skulls along with solid dates: L. Gabunia et al. (2000). “Earliest Pleistocene hominid cranial remains from Dmanisi, Republic of Georgia: Taxonomy, geological setting, and age.” Science 288 (5468): 1019–25.
uncovered yet another skull, the fourth from the area: D. Lordkipanidze et al. (2005). “The earliest toothless hominin skull.” Nature 434: 717–18.
Wild plants and game are nearly all hard to chew: Like nearly all else in human evolution, the need for teeth, or for help in the absence of them, is hotly debated. Some have argued that this unlucky soul might have soldiered on without help, mashing his food with stone tools or just choking down big chunks. It’s impossible to be certain. But it’s difficult for me to see how he could have survived, particularly through the serious illness, without help—much more help than apes give one another.
early primates coevolved with flowering plants: R. W. Sussman (1991). “Primate origins and the evolution of angiosperms.” Am. J. Primatol. 23 (4): 209–23.
hominin evolution lasted from seven to four million years ago: For a more thorough account of our species’ evolution than the short overview here, see Glenn C. Conroy and Herman Pontzer, Reconstructing Human Origins, 3rd ed. (W. W. Norton, 2012).
the topic of another larger book: Conroy and Pontzer, Reconstructing Human Origins.
stone tools from a 3.3-million-year-old site in northern Kenya: S. Harmand et al. (2015). “3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya.” Nature 521: 310–15.
Figure 4.1. The Human Family Tree: Adapted from Herman Pontzer (2017). “Economy and endurance in human evolution.” Curr. Biol. 27 (12): R613–21. doi: 10.1016/j.cub.2017.05.031.
animal fossils from sites in Kenya and Ethiopia show signs of butchery: M. Domínguez-Rodrigo, T. R. Pickering, S. Semaw, and M. J. Rogers (2005). “Cutmarked bones from Pliocene archaeological sites at Gona, Afar, Ethiopia: Implications for the function of the world’s oldest stone tools.” J. Hum. Evol. 48 (2): 109–21.
“to attack their prey, or otherwise to obtain food”: Charles Darwin, The Descent of Man (D. Appleton, 1871).
Orangutan mothers in the wild share food: A. V. Jaeggi, M. A. van Noordwijk, and C. P. van Schaik (2008). “Begging for information: Mother-offspring food sharing among wild Bornean orangutans.” Am. J. Primatol. 70 (6): 533–41. doi: 10.1002/ajp.20525.
Gorillas have never been observed sharing food: A. V. Jaeggi and C. P. Van Schaik (2011). “The evolution of food sharing in primates.” Behav. Ecol. Sociobiol. 65: 2125–40.
chimpanzees in the Sonso community in the Budongo Forest of Uganda: R. M. Wittig et al. (2014). “Food sharing is linked to urinary oxytocin levels and bonding in related and unrelated wild chimpanzees.” Proc. Biol. Sci. 281 (1778): 20133096. doi: 10.1098/rspb.2013.3096.
adult bonobos (mostly females) share a particular fruit: S. Yamamoto (2015). “Non-reciprocal but peaceful fruit sharing in wild bonobos in Wamba.” Behaviour 152: 335–57.
behaviors arise and the body adapts: A. Lister (2013). “Behavioural leads in evolution: Evidence from the fossil record.” Bio. J. Linnean Soc. 112: 315–31.
channel their maternal efforts into sharing food with their daughters: K. Hawkes et al. (1998). “Grandmothering, menopause, and the evolution of human life histories.” PNAS 95 (3): 1336–39. doi: 10.1073/pnas.95.3.1336.
fossil hominins with brains nearly 20 percent larger: S. C. Antón, R. Potts, and L. C. Aiello (2014). “Evolution of early Homo: An integrated biological perspective.” Science 345 (6192): 1236828. doi: 10.1126/science.1236828.
early members of the genus Homo were adapted for endurance running: D. M. Bramble and D. E. Lieberman (2004). “Endurance running and the evolution of Homo.” Nature 432: 345–52. doi: 10.1038/nature03052.
trade networks for highly prized raw materials stretch for miles: A. S. Brooks et al. (2018). “Long-distance stone transport and pigment use in the earliest Middle Stone Age.” Science 360 (6384): 90–94.
harvesting shellfish on an annual schedule: A. Jerardino, R. A. Navarro, and M. Galimberti (2014). “Changing collecting strategies of the clam Donax serra Röding (Bivalvia: Donacidae) during the Pleistocene at Pinnacle Point, South Africa.” J. Hum. Evol. 68: 58–67. doi: 10.1016/j.jhevol.2013.12.012.
murals on cave walls from Bordeaux to Borneo: M. Aubert et al. (2018). “Palaeolithic cave art in Borneo.” Nature 564: 254–57.
VO2 max, a common measure of peak aerobic power: H. Pontzer (2017). “Economy and endurance in human evolution.” Curr. Biol. 27 (12): R613–21. doi: 10.1016/j.cub.2017.05.031.
tool technology and hunting techniques were quite sophisticated: H. Thieme (1997). “Lower Palaeolithic hunting spears from Germany.” Nature 385: 807–10. doi: 10.1038/385807a0.
until late in their teenage years: H. Kaplan, K. Hill, J. Lancaster, and A. M. Hurtado (2000). “A theory of human life history evolution: Diet, intelligence, and longevity.” Evol. Anthro. 9 (4): 156–85.
interbirth intervals for chimpanzees, gorillas, and orangutans: M. E. Thompson (2013). “Comparative reproductive energetics of human and nonhuman primates.” Ann. Rev. Anthropol. 42: 287–304.
world was already full of strange and wonderful humanlike species: Nick Longrich, “Were other humans the first victims of the sixth mass extinction?” The Conversation, November 21, 2019, accessed March 16, 2020, https://theconversation.com/were-other-humans-the-first-victims-of-the-sixth-mass-extinction-126638.
bits of their DNA in our chromosomes today: S. Sankararaman, S. Mallick, N. Patterson, and D. Reich (2016). “The combined landscape of Denisovan and Neanderthal ancestry in present-day humans.” Curr. Biol. 26 (9): 1241–47. doi: 10.1016/j.cub.2016.03.037.
Neanderthals had brains a bit larger than ours and were making cave art, : D. L. Hoffmann et al. (2018). “U-Th dating of carbonate crusts reveals Neandertal origin of Iberian cave art.” Science 359 (6378): 912–15. doi: 10.1126/science.aap7778.
playing music: N. J. Conard, M. Malina, and S. C. Münzel (2009). “New flutes document the earliest musical tradition in southwestern Germany.” Nature 460: 737–40.
and burying their dead: W. Rendu et al. (2014). “Neandertal burial at La Chapelle-aux-Saints.” PNAS 111 (1): 81–86. doi: 10.1073/pnas.1316780110.
Homo sapiens became hyper-social through a long process: Brian Hare and Vanessa Woods, Survival of the Friendliest (Random House, 2020); Richard W. Wrangham, The Goodness Paradox (Pantheon, 2019).
they kill more people globally each year than violence: Risk Factors Collaborators (2016). “Global Burden of Disease 2015.” Lancet 388 (10053): 1659–1724.
by some accounts, human societies globally have become less violent: Steven Pinker, The Better Angels of Our Nature (Penguin, 2012).
Chimpanzees and bonobos put on less than 10 percent body fat: H. Pontzer et al. (2016). “Metabolic acceleration and the evolution of human brain size and life history.” Nature 533: 390–92.
hunter-gatherers like the Hadza put on more fat than that: H. Pontzer et al. (2012). “Hunter-gatherer energetics and human obesity.” PLoS One 7 (7): e40503. doi: 10.1371/journal.pone.0040503.
life as a hunter-gatherer is tough: For descriptions and data regarding Hadza life and daily activity, see Frank W. Marlowe, The Hadza: Hunter-Gatherers of Tanzania (Univ. of California Press, 2010); D. A. Raichlen et al. (2017). “Physical activity patterns and biomarkers of cardiovascular disease risk in hunter-gatherers.” Am. J. Hum. Biol. 29: e22919. doi: 10.1002/ajhb.22919.
hunter-gatherers lead lives that would make Westerners melt: H. Pontzer, B. M. Wood, and D. A. Raichlen (2018). “Hunter-gatherers as models in public health.” Obes. Rev. 19 (Suppl 1): 24–35.
Hadza data sat right on top of the measurements: H. Pontzer et al. (2012). “Hunter-gatherer energetics and human obesity.” PLoS One 7: e40503.
daily energy expenditures among five- to twelve-year-old Shuar kids: S. Urlacher et al. (2019). “Constraint and trade-offs regulate energy expenditure during childhood.” Science Advances 5 (12): eaax1065. doi: 10.1126/sciadv.aax1065.
daily energy expenditure in men and women among the Tsimane: M. D. Gurven et al. (2016). “High resting metabolic rate among Amazonian forager-horticulturalists experiencing high pathogen burden.” Am. J. Phys. Anth. 161 (3): 414–25. doi: 10.1002/ajpa.23040.
daily energy expenditures in black women from Maywood, Illinois, and rural Nigeria: K. E. Ebersole et al. (2008). “Energy expenditure and adiposity in Nigerian and African-American women.” Obesity 16 (9): 2148–54. doi: 10.1038/oby.2008.330.
same daily energy expenditures as pampered urbanites: L. R. Dugas et al. (2011). “Energy expenditure in adults living in developing compared with industrialized countries: A meta-analysis of doubly labeled water studies.” Am. J. Clin. Nutr. 93: 427–41.
no difference between moderately active adults and those with the highest levels: H. Pontzer et al. (2016). “Constrained total energy expenditure and metabolic adaptation to physical activity in adult humans.” Curr. Biol. 26 (3): 410–17. doi: 10.1016/j.cub.2015.12.046.
a year-long program to train them to run: K. R. Westerterp et al. (1992). “Long-term effect of physical activity on energy balance and body composition.” Brit. J. Nutr. 68: 21–30.
were running roughly 25 miles per week: The protocol was described as 60 minutes per session, 4 days a week, which would be about 25 miles per week at a 9:36 minutes/mile pace.
the rule among warm-blooded animals: H. Pontzer (2015). “Constrained total energy expenditure and the evolutionary biology of energy balance.” Exer. Sport. Sci. Rev. 43: 110–16; T. J. O’Neal et al. (2017). “Increases in physical activity result in diminishing increments in daily energy expenditure in mice.” Curr. Biol. 27 (3): 423–30.
Same goes for kangaroos and pandas: H. Pontzer et al. (2014). “Primate energy expenditure and life history.” PNAS 111 (4): 1433–37; Y. Nie et al. (2015). “Exceptionally low daily energy expenditure in the bamboo-eating giant panda.” Science 349 (6244): 171–74.
daily energy expenditures and the PAL ratio have stayed the same: K. R. Westerterp and J. R. Speakman (2008). “Physical activity energy expenditure has not declined since the 1980s and matches energy expenditures of wild mammals.” Internat. J. Obesity 32: 1256–63.
Midwest Exercise Trial 1 study conducted: J. E. Donnelly et al. (2003). “Effects of a 16-month randomized controlled exercise trial on body weight and composition in young, overweight men and women: The Midwest Exercise Trial.” Arch. Intern. Med. 163 (11): 1343–50.
a more demanding workout regime in Midwest 2: S. D. Herrmann et al. (2015). “Energy intake, nonexercise physical activity, and weight loss in responders and nonresponders: The Midwest Exercise Trial 2.” Obesity 23 (8):1539–49. doi: 10.1002/oby.21073.
two years, the average amount of weight lost is less than five pounds: D. L. Swift et al. (2014). “The role of exercise and physical activity in weight loss and maintenance.” Prog. Cardiov. Dis. 56 (4): 441–47. doi: 10.1016/j.pcad.2013.09.012.
elevated daily expenditures in a small sample of Shuar men: L. Christopher et al. (2019). “High energy requirements and water throughput of adult Shuar forager-horticulturalists of Amazonian Ecuador.” Am. J. Hum. Biol. 31: e23223. doi: 10.1002/ajhb.23223.
Obese people burn just as much energy each day: D. A. Schoeller (1999). “Recent advances from application of doubly labeled water to measurement of human energy expenditure.” J. Nutr. 129: 1765–68.
children have shown the same result: S. R. Zinkel et al. (2016). “High energy expenditure is not protective against increased adiposity in children.” Pediatr. Obes. 11 (6): 528–34. doi: 10.1111/ijpo.12099.
study metabolic changes among Biggest Loser contestants: D. L. Johannsen et al. (2012). “Metabolic slowing with massive weight loss despite preservation of fat-free mass.” J. Clin. Endocrinol. Metab. 97 (7): 2489–96. doi: 10.1210/jc.2012-1444.
their BMRs were still lower than expected: E. Fothergill et al. (2016). “Persistent metabolic adaptation 6 years after ‘The Biggest Loser’ competition.” Obesity 24 (8): 1612–19. doi: 10.1002/oby.21538.
studies was conducted in 1917 by Francis Benedict: F. G. Benedict (1918). “Physiological effects of a prolonged reduction in diet on twenty-five men.” Proc. Am. Phil. Soc. 57 (5): 479–90.
Ancel Keys and colleagues at the University of Minnesota: Ancel Keys, Josef Brozek, and Austin Henschel, The Biology of Human Starvation, vol. 1 (Univ. of Minnesota Press, 1950).
overshooting phenomenon isn’t as well studied: A. G. Dulloo, J. Jacquet, and L. Girardier (1997). “Poststarvation hyperphagia and body fat overshooting in humans: A role for feedback signals from lean and fat tissues.” Am. J. Clin. Nutr. 65 (3): 717–23.
metabolic manager isn’t just a metaphor or a cartoon: For an excellent review of the neural control of hunger and satiety, read Stephan Guyenet, The Hungry Brain: Outsmarting the Instincts That Make Us Overeat (Flatiron Books, 2017).
thyroid hormone, the main control hormone for our metabolic rate: L. M. Redman and E. Ravussin (2009). “Endocrine alterations in response to calorie restriction in humans.” Mol. Cell. Endocrin. 299 (1): 129–36. doi: 10.1016/j.mce.2008.10.014.
humans are quick to put reproduction on the back burner: For a thorough discussion of the role of energy availability in human reproduction, see Peter Ellison, On Fertile Ground (Harvard Univ. Press, 2003).
food restriction is sufficiently severe, will stop ovulating: N. I. Williams et al. (2010). “Estrogen and progesterone exposure is reduced in response to energy deficiency in women aged 25–40 years.” Hum. Repro. 25 (9): 2328–39. doi: 10.1093/humrep/deq172.
mice faced with starvation maintain two organs: S. E. Mitchell et al. (2015). “The effects of graded levels of calorie restriction: I. Impact of short term calorie and protein restriction on body composition in the C57BL/6 mouse.” Oncotarget 6: 15902–30.
body weights and BMIs hardly change: H. Pontzer, B. M. Wood, and D. A. Raichlen (2018). “Hunter-gatherers as models in public health.” Obes. Rev. 19 (Suppl 1): 24–35.
our body tries to make use of some: R. L. Leibel, M. Rosenbaum, and J. Hirsch (1995). “Changes in energy expenditure resulting from altered body weight.” N. Engl. J. Med. 332 (10): 621–28.
the average American adult gains about half a pound: S. Stenholm et al. (2015). “Patterns of weight gain in middle-aged and older US adults, 1992–2010.” Epidemiology 26 (2): 165–68. doi: 10.1097/EDE.0000000000000228.
gain weight around the holidays: E. E. Helander, B. Wansink, and A. Chieh (2016). “Weight gain over the holidays in three countries.” N. Engl. J. Med. 375 (12): 1200–02. doi: 10.1056/NEJMc1602012.
moths mistaking a porch light for the moon: R. Hertzberg, “Why insects like moths are so attracted to bright lights.” National Geographic, October 5, 2018, accessed March 18, 2020, https://www.nationalgeographic.com/animals/2018/10/moth-meme-lamps-insects-lights-attraction-news/.
the venerable Weight Watchers: “Dieters move away from calorie obsession,” CBS, April 12, 2014, https://www.cbsnews.com/news/dieters-move-away-from-calorie-obsession/.
European taxonomists named it Indicator indicator: It was originally named Cuculus indicator because honeyguides lay their eggs in other birds’ nests, cuckolding the unwitting parents. See A. Spaarman, “An account of a journey into Africa from the Cape of Good-Hope, and a description of a new species of cuckow.” Phil. Trans. Roy. Soc. London (Royal Society of London, 1777), 38–47.
honeyguide split from the other species: B. M. Wood et al. (2014). “Mutualism and manipulation in Hadza–honeyguide interactions.” Evol. Hum. Behav. 35: 540–46.
the Dunning-Kruger effect: J. Kruger and D. Dunning (1999). “Unskilled and unaware of it: How difficulties in recognizing one’s own incompetence lead to inflated self-assessments.” J. Pers. Soc. Psych. 77 (6): 1121–34.
“ignorance more frequently begets confidence than does knowledge”: Charles Darwin, Descent of Man (John Murray & Sons, 1871), 3.
competence in governing and expertise in world affairs: Could you tell this was a joke? If not, you might be a victim of the Dunning-Kruger effect.
talking points from PETA: “Is It Really Natural? The Truth About Humans and Eating Meat,” PETA, January 23, 2018, accessed March 18, 2020, https://www.peta.org/living/food/really-natural-truth-humans-eating-meat/.
our hominin ancestors got their start: H. Pontzer (2012). “Overview of hominin evolution.” Nature Education Knowledge 3 (10): 8, accessed March 18, 2020, https://www.nature.com/scitable/knowledge/library/overview-of-hominin-evolution-89010983/.
Insects might have been a regular part of the menu: L. R. Backwell and F. d’Errico (2001). “Evidence of termite foraging by Swartkrans early hominids.” PNAS 98 (4): 1358–63. doi: 10.1073/pnas.021551598.
the exploitation of tubers: G. Laden and R. Wrangham (2005). “The rise of the hominids as an adaptive shift in fallback foods: Plant underground storage organs (USOs) and australopith origins.” J. Hum. Evol. 49 (4): 482–98.
the telltale isotopic signatures of their bones: K. Jaouen et al. (2019). “Exceptionally high δ15N values in collagen single amino acids confirm Neandertals as high-trophic level carnivores.” PNAS 116 (11): 4928–33. doi: 10.1073/pnas.1814087116.
our digestive tracts are 40 percent smaller: L. C. Aiello and P. Wheeler (1995). “The expensive tissue hypothesis: The brain and the digestive system in human and primate evolution.” Curr. Anthropol. 36: 199–221.
but they balanced all that meat with carb-rich grains: A. G. Henry, A. S. Brooks, and D. R. Piperno (2014). “Plant foods and the dietary ecology of Neanderthals and early modern humans.” J. Hum. Evol. 69: 44–54; R. C. Power et al. (2018). “Dental calculus indicates widespread plant use within the stable Neanderthal dietary niche.” J. Hum. Evol. 119: 27–41.
bread remnants dated to over 14,000 years ago: A. Arranz-Otaegui et al. (2018). “Archaeobotanical evidence reveals the origins of bread 14,400 years ago in northeastern Jordan.” PNAS 115 (31): 7925–30. doi: 10.1073/pnas.1801071115.
the anthropologist George Murdock in his Ethnographic Atlas: G. P. Murdock, Ethnographic Atlas (Univ. Pittsburgh Press, 1967).
pillaging rodent burrows to steal their stores: S. Ståhlberg and I. Svanberg (2010). “Gathering food from rodent nests in Siberia.” J. Ethnobiol. 30 (2): 184–202.
blood sugar and fat metabolism respond identically to honey: S. K. Raatz, L. K. Johnson, and M. J. Picklo (2015). “Consumption of honey, sucrose, and high-fructose corn syrup produces similar metabolic effects in glucose-tolerant and -intolerant individuals.” J. Nutr. 145 (10): 2265–72. doi: 10.3945/jn.115.218016.
they have exceptionally healthy hearts: H. Pontzer, B. M. Wood, and D. A. Raichlen (2018). “Hunter-gatherers as models in public health.” Obes. Rev. 19 (Suppl 1): 24–35.
ancestral diet was only 5 percent carbs and 75 percent fat!: David Perlmutter, Grain Brain: The Surprising Truth About Wheat, Carbs, and Sugar (Little, Brown Spark, 2013), 35.
These analyses spawned a number of peer-reviewed scientific papers: L. Cordain et al. (2000). “Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets.” Am. J. Clin. Nutr. 71: 682–92.
Cordain’s influential book, The Paleo Diet: Loren Cordain, The Paleo Diet (John Wiley & Sons, 2002).
Phinney, a doctor, biochemist, and vocal advocate: S. D. Phinney (2004). “Ketogenic diets and physical performance.” Nutr. Metab. (London) 1 (2). doi: 10.1186/1743-7075-1-2.
gets going only around 6,500 years ago in Africa: B. S. Arbuckle and E. L. Hammer (2018). “The rise of pastoralism in the ancient Near East.” J. Archaeol. Res. 27: 391–449. doi: 10.1007/s10814-018-9124-8.
bison-hunting cultures of the Plains weren’t established: D. G. Bamforth (2011). “Origin stories, archaeological evidence, and post-Clovis Paleoindian bison hunting on the Great Plains.” American Antiquity 76 (1): 24–40.
Arctic cultures are even a bit younger: “Inuit Ancestor Archaeology: The Earliest Times.” CHIN, 2000, accessed March 18, 2020, http://www.virtualmuseum.ca/edu/ViewLoitLo.do?method=preview&lang=EN&id=10101.
diets in populations like the Hadza, Tsimane, Shuar: H. Pontzer, B. M. Wood, and D. A. Raichlen (2018). “Hunter-gatherers as models in public health.” Obes. Rev. 19 (Suppl 1): 24–35; L. Christopher et al. (2019). “High energy requirements and water throughput of adult Shuar forager-horticulturalists of Amazonian Ecuador.” Am. J. Hum. Biol. 31: e23223. doi: 10.1002/ajhb.23223.
happened twice, independently, among early pastoralist groups: S. A. Tishkoff et al. (2007). “Convergent adaptation of human lactase persistence in Africa and Europe.” Nature Genetics 39 (1): 31–40. doi: 10.1038/ng1946
humans have more copies of the gene that makes salivary amylase: G. H. Perry et al. (2007). “Diet and the evolution of human amylase gene copy number variation.” Nature Genetics 39 (10): 1256–60. doi: 10.1038/ng2123.
decreasing levels of dietary folate: A. Sabbagh et al. (2011). “Arylamine N-acetyltransferase 2 (NAT2) genetic diversity and traditional subsistence: A worldwide population survey.” PloS One 6 (4): e18507. doi: 10.1371/journal.pone.0018507.
changes in the fatty acid desaturase genes (FADS1 and 2): S. Mathieson and I. Mathieson (2018). “FADS1 and the timing of human adaptation to agriculture.” Mol. Biol. Evol. 35 (12): 2957–70. doi: 10.1093/molbev/msy180.
high levels of arsenic in their groundwater: M. Apata, B. Arriaza, E. Llop, and M. Moraga (2017). “Human adaptation to arsenic in Andean populations of the Atacama Desert.” Am. J. Phys. Anthropol. 163 (1): 192–99. doi: 10.1002/ajpa.23193. Epub 2017 Feb 16.
FADS genes have changed in these groups as well: M. Fumagalli et al. (2015). “Greenlandic Inuit show genetic signatures of diet and climate adaptation.” Science 349 (6254): 1343–47.
most people in these groups can’t go into ketosis: F. J. Clemente et al. (2014). “A selective sweep on a deleterious mutation in CPT1A in Arctic populations.” Am. J. Hum. Gen. 95 (5): 584–89. doi: 10.1016/j.ajhg.2014.09.016.
Dr. Oz is pushing “detox water”: “Dr. Oz’s detox water,” Women’s World Magazine, May 27, 2019.
“Negative calorie” foods that supposedly take more energy to digest: M. E. Clegg and C. Cooper (2012). “Exploring the myth: Does eating celery result in a negative energy balance?” Proc. Nutr. Soc. 71 (oce3): e217.
ice water won’t change the amount of energy you burn: There’s no evidence that the body burns extra energy to warm up ice water. Even if it did, the 240 ml in a glass of ice water (0°C) would only require 240 × 37 = 8,880 calories to warm up to body temp, or about 9 kcal.
caffeine in a cup of coffee: A. G. Dulloo et al. (1989). “Normal caffeine consumption: Influence on thermogenesis and daily energy expenditure in lean and postobese human volunteers.” Am. J. Clin. Nutr. 49 (1): 44–50.
saturated fats and trans fats as important risk factors: L. Hooper, N. Martin, A. Abdelhamid, and G. D. Smith (2015). “Reduction in saturated fat intake for cardiovascular disease.” Cochrane Database Syst. Rev. 6: CD011737. doi: 10.1002/14651858.CD011737; F. M. Sacks et al. (2017). “Dietary fats and cardiovascular disease: A presidential advisory from the American Heart Association.” Circulation 136 (3): e1–e23. doi: 10.1161/CIR.0000000000000510.
cookbook promoting them, The Benevolent Bean: Margaret Keys and Ancel Keys, The Benevolent Bean (Doubleday, 1967).
insulin stimulates the conversion of excess glucose into fat: K. N. Frayn et al. (2003). “Integrative physiology of human adipose tissue.” Int. J. Obes. Relat. Metab. Disord. 27: 875–88.
accumulation of fat is the cause of overeating: D. S. Ludwig and M. I. Friedman (2014). “Increasing adiposity: Consequence or cause of overeating?” JAMA 311: 2167–68.
Hall’s team kept men who were overweight or obese: K. D. Hall et al. (2016). “Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men.” Am. J. Clin. Nutr. 104 (2): 324–33. doi: 10.3945/ajcn.116.133561.
achieved either through cutting carbs or cutting fat: K. D. Hall et al. (2015). “Calorie for calorie, dietary fat restriction results in more body fat loss than carbohydrate restriction in people with obesity.” Cell Metabolism 22 (3): 427–36. doi: 10.1016/j.cmet.2015.07.021.
no difference in daily energy expenditure: W. G. Abbott, B. V. Howard, G. Ruotolo, and E. Ravussin (1990). “Energy expenditure in humans: Effects of dietary fat and carbohydrate.” Am. J. Physiol. 258 (2 Pt 1): E347–51.
DIETFITS study . . . randomly assigned 609 men and women: C. D. Gardner et al. (2018). “Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion: The DIETFITS randomized clinical trial.” JAMA 319 (7): 667–79. doi: 10.1001/jama.2018.0245.
In the 1960s and ’70s, when John Yudkin: John Yudkin, Pure, White and Deadly: The Problem of Sugar (Davis-Poynter, 1972).
Heart disease deaths, while still alarmingly high: H. K. Weir et al. (2016). “Heart disease and cancer deaths: Trends and projections in the United States, 1969–2020.” Prev. Chron. Dis. 13: 160211.
the prevalence of overweight, obesity: C. D. Fryar, M. D. Carroll, and C. L. Ogden, “Prevalence of Overweight, Obesity, and Extreme Obesity Among Adults Aged 20 and Over: United States, 1960–1962 Through 2013–2014,” Centers for Disease Control and Prevention, July 18, 2016, accessed March 18, 2020, https://www.cdc.gov/nchs/data/hestat/obesity_adult_13_14/obesity_adult_13_14.htm.
diabetes have continued to climb: CDC’s Division of Diabetes Translation, “Long-term Trends in Diabetes April 2017,” April 2017, accessed March 18, 2020, https://www.cdc.gov/diabetes/statistics/slides/long_term_trends.pdf.
even as people eat less sugar: “Food Availability (Per Capita) Data System,” USDA Economic Research Service, last updated January 9, 2020, accessed March 18, 2020, https://www.ers.usda.gov/data-products/food-availability-per-capita-data-system/.
In China, the percentage of calories from fats has risen: J. Zhao et al. (2018). “Secular trends in energy and macronutrient intakes and distribution among adult females (1991–2015): Results from the China Health and Nutrition Survey.” Nutrients 10 (2): 115.
obesity and diabetes have steadily climbed: R. C. W. Ma (2018). “Epidemiology of diabetes and diabetic complications in China.” Diabetologia 61: 1249–60. doi: 10.1007/s00125-018-4557-7.
obesity and metabolic disease have taken hold: T. Bhurosy and R. Jeewon (2014). “Overweight and obesity epidemic in developing countries: A problem with diet, physical activity, or socioeconomic status?” Sci. World J. 2014: 964236. doi: 10.1155/2014/964236.
Ludwig and colleagues examined metabolic rates: C. B. Ebbeling et al. (2018). “Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: Randomized trial.” BMJ (Clinical research ed.) 363: k4583. doi: 10.1136/bmj.k4583.
reanalysis of their data by Kevin Hall: K. D. Hall (2019). “Mystery or method? Evaluating claims of increased energy expenditure during a ketogenic diet.” PloS One 14 (12): e0225944. doi: 10.1371/journal.pone.0225944.
the ratio of carbs to fats has little or no effect: K. D. Hall and J. Guo (2017). “Obesity energetics: Body weight regulation and the effects of diet composition.” Gastroenterology 152 (7): 1718–27.e3. doi: 10.1053/j.gastro.2017.01.052.
calories from sugar (including high fructose corn syrup): T. A. Khan, and J. L Sievenpiper (2016). “Controversies about sugars: Results from systematic reviews and meta-analyses on obesity, cardiometabolic disease and diabetes.” Eur. J. Nutr. 55 (Suppl 2): 25–43. doi: 10.1007/s00394-016-1345-3.
leads to water loss and a rapid reduction in body weight: S. N. Kreitzman, A. Y. Coxon, and K. F. Szaz (1992). “Glycogen storage: Illusions of easy weight loss, excessive weight regain, and distortions in estimates of body composition.” Am. J. Clin. Nutr. 56 (1 Suppl): 292S–93S. doi: 10.1093/ajcn/56.1.292S.
one of four popular diets for twelve months: M. L. Dansinger et al. (2005). “Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: A randomized trial.” JAMA 293 (1): 43–53. doi: 10.1001/jama.293.1.43.
Penn Jillette reportedly lost more than a hundred pounds: Susan Rinkunas, “Eating Only One Food to Lose Weight Is a Terrible Idea,” The Cut, August 16, 2009, accessed March 18, 2020, https://www.thecut.com/2016/08/mono-diet-potato-diet-penn-jillette.html.
followed a junk food diet for ten weeks: Madison Park, “Twinkie diet helps nutrition professor lose 27 pounds,” CNN, November 8, 2010, http://www.cnn.com/2010/HEALTH/11/08/twinkie.diet.professor/index.html.
low-carb diets were used to treat diabetes: William Morgan, Diabetes Mellitus: Its History, Chemistry, Anatomy, Pathology, Physiology, and Treatment (The Homoeopathic Publishing Company, 1877).
eliminated their need for insulin and other diabetes medication: S. J. Athinarayanan et al. (2019). “Long-term effects of a novel continuous remote care intervention including nutritional ketosis for the management of type 2 diabetes: A 2-year non-randomized clinical trial.” Fron. Endocrinol. 10: 348. doi: 10.3389/fendo.2019.00348.
weight loss can reverse type 2 diabetes: R. Taylor, A. Al-Mrabeh, and N. Sattar (2019). “Understanding the mechanisms of reversal of type 2 diabetes.” Lancet Diab. Endocrinol. 7 (9): 726–36. doi: 10.1016/S2213-8587(19)30076-2.
intermittent fasting diets are no more successful: I. Cioffi et al. (2018). “Intermittent versus continuous energy restriction on weight loss and cardiometabolic outcomes: A systematic review and meta-analysis of randomized controlled trials.” J. Transl. Med. 16: 371. doi: 10.1186/s12967-018-1748-4.
a thorough and engaging book, The Hungry Brain: Stephan Guyenet, The Hungry Brain: Outsmarting the Instincts That Make Us Overeat (Flatiron Books, 2017).
respond strongly to food, particularly fat and sugar: M. Alonso-Alonso et al. (2015). “Food reward system: Current perspectives and future research needs.” Nutr. Rev. 73 (5): 296–307. doi: 10.1093/nutrit/nuv002.
Protein intake is monitored as well: M. Journel et al. (2012). “Brain responses to high-protein diets.” Advances in Nutrition (Bethesda, Md.) 3 (3): 322–29. doi: 10.3945/an.112.002071.
which communicates with the hypothalamus: K. Timper and J. C. Brüning (2017). “Hypothalamic circuits regulating appetite and energy homeostasis: Pathways to obesity.” Disease Models & Mechanisms 10 (6): 679–89. doi: 10.1242/dmm.026609.
they will inevitably overeat and get fat: A. Sclafani and D, Springer (1976). “Dietary obesity in adult rats: Similarities to hypothalamic and human obesity syndromes.” Physiol. Behav. 17 (3): 461–71.
from monkeys to elephants, and, unsurprisingly, in humans: Monkeys: P. B. Higgins et al. (2010). “Eight week exposure to a high sugar high fat diet results in adiposity gain and alterations in metabolic biomarkers in baboons (Papio hamadryas sp.).” Cardiovasc. Diabetol. 9: 71. doi: 10.1186/1475-2840-9-71; Elephants: K. A. Morfeld, C. L. Meehan, J. N. Hogan, and J. L. Brown (2016). “Assessment of body condition in African (Loxodonta africana) and Asian (Elephas maximus) elephants in North American zoos and management practices associated with high body condition scores.” PLoS One 11: e0155146. doi: 10.1371/journal.pone.0155146; Humans: R. Rising et al. (1992). “Food intake measured by an automated food-selection system: Relationship to energy expenditure.” Am. J. Clin. Nutr. 55 (2): 343–49.
sugars and oils are the two leading sources of calories: S. A. Bowman et al., “Retail Food Commodity Intakes: Mean Amounts of Retail Commodities per Individual, 2007–08,” USDA Agricultural Research Service and USDA Economic Research Service, 2013.
foods that always leave you wanting more: George Dvorsky, “How Flavor Chemists Make Your Food So Addictively Good,” Gizmodo, November 8, 2012, accessed March 18, 2020, https://io9.gizmodo.com/how-flavor-chemists-make-your-food-so-addictively-good-5958880.
just how powerful processed foods can be: K. D. Hall et al. (2019). “Ultra-processed diets cause excess calorie intake and weight gain: An inpatient randomized controlled trial of ad libitum food intake.” Cell Metabol. 30 (1): 67–77.e3.
explains the increase in the average weight: S. H. Holt, J. C. Miller, P. Petocz, and E. Farmakalidis (1995). “A satiety index of common foods.” Eur. J. Clin. Nutr. 49 (9): 675–90.
they gain similar amounts of fat: C. Bouchard et al. (1990). “The response to long-term overfeeding in identical twins.” N. Engl. J. Med. 322 (21): 1477–82.
Twins respond in similar ways to underfeeding: A. Tremblay et al. (1997). “Endurance training with constant energy intake in identical twins: Changes over time in energy expenditure and related hormones.” Metabolism 46 (5): 499–503.
nine hundred gene variants associated with obesity: L. Yengo et al. and the GIANT Consortium (2018). “Meta-analysis of genome-wide association studies for height and body mass index in ~700000 individuals of European ancestry.” Hum. Mol. Gen. 27 (20): 3641–49. doi: 10.1093/hmg/ddy271.
in 1995 tested thirty-eight different foods: S. H. Holt, J. C. Miller, P. Petocz, and E. Farmakalidis (1995). “A satiety index of common foods.” Eur. J. Clin. Nutr. 49 (9): 675–90.
people eat more after a stressful experience: B. Hitze et al. (2010). “How the selfish brain organizes its supply and demand.” Frontiers in Neuroenergetics 2: 7. doi: 10.3389/fnene.2010.00007.
gain an average of one to two pounds over the holidays: E. E. Helander, B. Wansink, and A. Chieh (2016). “Weight gain over the holidays in three countries.” N. Engl. J. Med. 375 (12): 1200–2. doi: 10.1056/NEJMc1602012.
poverty and lack of opportunity are so strongly associated: K. A. Scott, S. J. Melhorn, and R. R. Sakai (2012). “Effects of chronic social stress on obesity.” Curr. Obes. Rep. 1: 16–25.
Hadza eat about five times as much fiber each day: H. Pontzer, B. M. Wood, and D. A. Raichlen (2018). “Hunter-gatherers as models in public health.” Obes. Rev. 19 (Suppl 1): 24–35.
which likely helps protect them against heart disease: L. Hooper, N. Martin, A. Abdelhamid, and G. D. Smith (2015). “Reduction in saturated fat intake for cardiovascular disease.” Cochrane Database Syst. Rev. 6: CD011737. doi: 10.1002/14651858.CD011737.
great apes get nine or ten hours of sleep each night: C. L. Nunn and D. R. Samson (2018). “Sleep in a comparative context: Investigating how human sleep differs from sleep in other primates.” Am. J. Phys. Anthropol. 166 (3): 601–12.
chimpanzees climb about 330 feet per day: H. Pontzer and R. W. Wrangham (2014). “Climbing and the daily energy cost of locomotion in wild chimpanzees: Implications for hominoid locomotor evolution.” J. Hum. Evol. 46 (3): 317–35.
Apes don’t develop hardened vessels or have heart attacks: K. Kawanishi et al. (2019). “Human species-specific loss of CMP-N-acetylneuraminic acid hydroxylase enhances atherosclerosis via intrinsic and extrinsic mechanisms.” PNAS 116 (32): 16036–45. doi: 10.1073/pnas.1902902116.
men who can do more than ten pushups in one go: Justin Yang et al. (2019). “Association between push-up exercise capacity and future cardiovascular events among active adult men.” JAMA Network Open 2 (2): e188341. doi: 10.1001/jamanetworkopen.2018.8341.
Older adults who can cover at least 1,200 feet: A. Yazdanyar et al. (2014) “Association between 6-minute walk test and all-cause mortality, coronary heart disease-specific mortality, and incident coronary heart disease.” Journal of Aging and Health 26 (4): 583–99. doi: 10.1177/0898264314525665.
Vigorous activity, defined as anything demanding 6 METS: “Examples of Moderate and Vigorous Physical Activity,” Harvard T. H. Chan School of Public Health, accessed March 20, 2020, https://www.hsph.harvard.edu/obesity-prevention-source/moderate-and-vigorous-physical-activity/.
triggering the release of nitric oxide: G. Schuler, V. Adams, and Y. Goto (2013). “Role of exercise in the prevention of cardiovascular disease: Results, mechanisms, and new perspectives.” Eur. Heart J. 34: 1790–99.
slowing the rate of cognitive decline: G. Kennedy et al. (2017). “How does exercise reduce the rate of age-associated cognitive decline? A review of potential mechanisms.” J. Alzheimers Dis. 55 (1): 1–18. doi: 10.3233/JAD-160665.
walking and running improve cognitive function: D. A. Raichlen and G. E. Alexander (2017). “Adaptive capacity: An evolutionary neuroscience model linking exercise, cognition, and brain health.” Trends Neurosci. 40 (7): 408–21. doi: 10.1016/j.tins.2017.05.001.
Dan Lieberman, my PhD advisor at Harvard, details in his book Exercised: Daniel Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding (Pantheon, 2020).
exercising muscles release hundreds of molecules: M. Whitham et al. (2018). “Extracellular vesicles provide a means for tissue crosstalk during exercise.” Cell Metab. 27 (1): 237–51.e4.
subjected adult male mice to different degrees of calorie restriction: S. E. Mitchell et al. (2015). “The effects of graded levels of calorie restriction: I. Impact of short term calorie and protein restriction on body composition in the C57BL/6 mouse.” Oncotarget 6: 15902–30.
children fighting an infection increase the energy spent: S. S. Urlacher et al. (2018). “Tradeoffs between immune function and childhood growth among Amazonian forager-horticulturalists.” PNAS 115 (17): E3914–21. doi: 10.1073/pnas.1717522115.
When exercise starts to take up a large chunk: H. Pontzer (2018). “Energy constraint as a novel mechanism linking exercise and health.” Physiology 33 (6): 384–93.
exercise is an effective way to lower chronic inflammation: M. Gleeson et al. (2011). “The anti-inflammatory effects of exercise: Mechanisms and implications for the prevention and treatment of disease.” Nat. Rev. Immunol. 11: 607–15.
used public speaking to induce a stress response: U. Rimmele et al. (2007). “Trained men show lower cortisol, heart rate and psychological responses to psychosocial stress compared with untrained men.” Psychoneuroendocrinology 32: 627–35.
a study of college-age women with moderate depression: C. Nabkasorn et al. (2006). “Effects of physical exercise on depression, neuroendocrine stress hormones and physiological fitness in adolescent females with depressive symptoms.” Eur. J. Publ. Health 16: 179–84.
endurance runners to age-matched sedentary men: A. C. Hackney (2020). “Hypogonadism in exercising males: Dysfunction or adaptive-regulatory adjustment?” Front. Endocrinol. 11: 11. doi: 10.3389/fendo.2020.00011.
most effective ways to decrease the risk of cancers: J. C. Brown, K. Winters-Stone, A. Lee, and K. H. Schmitz (2012). “Cancer, physical activity, and exercise.” Compr Physiol. 2: 2775–809.
doping was present at the birth of competitive cycling: Lorella Vittozzi, “Historical Evolution of the Doping Phenomenon,” Report on the I.O.A.’s Special Sessions and Seminars 1997, International Olympic Academy, 1997, 68–70.
testosterone and its synthetic relatives accounted for 45 percent: R. I. Wood and S. J. Stanton (2012). “Testosterone and sport: Current perspectives.” Horm. Behav. 61 (1): 147–55. doi: 10.1016/j.yhbeh.2011.09.010.
food supplements to thirty-one women endurance athletes: K. Lagowska, K. Kapczuk, Z. Friebe, and J. Bajerska (2014). “Effects of dietary intervention in young female athletes with menstrual disorders.” J. Int. Soc. Sports Nutr. 11: 21.
Hadza men and women average around 16,000 steps: B. M. Wood et al. (2018). “Step counts from satellites: Methods for integrating accelerometer and GPS data for more accurate measures of pedestrian travel.” J. Meas. Phys. Behav. 3 (1): 58–66.
rack up less than two hours of physical activity: Estimated amount of time to cover their customary 2 to 3 km per day walking and about 100 meters climbing: H. Pontzer. “Locomotor Ecology and Evolution in Chimpanzees and Humans.” In Martin N. Muller, Richard W. Wrangham, and David R. Pilbeam, eds., Chimpanzees in Human Evolution (Harvard Univ. Press, 2017), 259–85.
They average around 5,000 steps per day: Chimpanzees cover roughly half a meter per step: H. Pontzer, D. A. Raichlen, and P. S. Rodman (2014). “Bipedal and quadrupedal locomotion in chimpanzees.” J. Hum. Evol. 66: 64–82.
followed nearly 5,000 U.S. adults for five to eight years: P. F. Saint-Maurice et al. (2018). “Moderate-to-vigorous physical activity and all-cause mortality: Do bouts matter?” J. Am. Heart Assoc. 7(6): e007678. doi: 10.1161/JAHA.117.007678.
study of 150,000 Australian adults: E. Stamatakis et al. (2019). “Sitting time, physical activity, and risk of mortality in adults.” J. Am. Coll. Cardiol. 73 (16): 2062–72. doi: 10.1016/j.jacc.2019.02.031.
the famed Copenhagen City Heart Study: P. Schnohr et al. (2015). “Dose of jogging and long-term mortality: The Copenhagen City Heart Study.” J. Am. Coll. Cardiol. 65 (5): 411–19. doi: 10.1016/j.jacc.2014.11.023.
a study of postal workers in Glasgow: W. Tigbe, M. Granat, N. Sattar, and M. Lean (2017). “Time spent in sedentary posture is associated with waist circumference and cardiovascular risk.” Int. J. Obes. 41: 689–96. doi: 10.1038/ijo.2017.30.
one of the lowest life expectancies in Western Europe: “Scotland’s public health priorities,” Scottish Government, Population Health Directorate, 2018, accessed March 20, 2020, https://www.gov.scot/publications/scotlands-public-health-priorities/pages/2/.
traditional populations sleep about as much: G. Yetish et al. (2015) “Natural sleep and its seasonal variations in three pre-industrial societies.” Curr. Biol. 25 (21): 2862–68. doi: 10.1016/j.cub.2015.09.046.
increase our risk of cardiometabolic disease: A. W. McHill et al. (2014) “Impact of circadian misalignment on energy metabolism during simulated nightshift work.” PNAS 111 (48): 17302–07. doi: 10.1073/pnas.1412021111.
Hadza adults also accumulate the same amount of resting: D. A. Raichlen et al. (2020) “Sitting, squatting, and the evolutionary biology of human inactivity.” PNAS, Epub ahead of print. doi: 10.1073/pnas.1911868117.
billionaire recluse who lives for months in the dark: Wikipedia, accessed March 20, 2020, https://en.wikipedia.org/wiki/Howard_Hughes.
teamed up with a dietician and medical officer: J. Mayer, P. Roy, and K. P. Mitra (1956). “Relation between caloric intake, body weight, and physical work: Studies in an industrial male population in West Bengal.” Am. J. Clin. Nutr. 4 (2): 169–75.
followed nearly two thousand men and women: L. R. Dugas et al. (2017). “Accelerometer-measured physical activity is not associated with two-year weight change in African-origin adults from five diverse populations.” Peer J. 5: e2902. doi: 10.7717/peerj.2902.
the brain regulates hunger and metabolism: A. Prentice and S. Jebb (2004). “Energy intake/physical activity interactions in the homeostasis of body weight regulation.” Nutr. Rev. 62: S98–104.
attributable to sedentary lifestyles: I. Lee et al. (2012). “Effect of physical inactivity on major non-communicable diseases worldwide: An analysis of burden of disease and life expectancy.” Lancet (London) 380 (9838): 219–29. doi: 10.1016/S0140-6736(12)61031-9.
a study of obese policemen in Boston: K. Pavlou, S. Krey, and W. P. Steffee (1989). “Exercise as an adjunct to weight loss and maintenance in moderately obese subjects.” Am. J. Clin. Nutr. 49: 1115–23.
National Weight Control Registry: “The National Weight Control Registry,” accessed March 20, 2020, http://www.nwcr.ws/.
Registry members spent nearly an hour more each day: D. M. Ostendorf et al. (2018). “Objectively measured physical activity and sedentary behavior in successful weight loss maintainers.” Obesity 26 (1): 53–60. doi: 10.1002/oby.22052.
only eight had completed the crossing: Ocean Rowing, “Atlantic Ocean Crossings West–East from Canada,” August 4, 2018, accessed March 21, 2020, http://www.oceanrowing.com/statistics/Atlantic_W-E__from_Canada.htm.
Bryce ate between 4,000 and 5,000 kilocalories: Christopher Mele, “Ohio teacher sets record for rowing alone across the Atlantic,” New York Times, August 6, 2018, accessed March 21, 2020, https://www.nytimes.com/2018/08/06/world/bryce-carlson-rows-atlantic-ocean.html.
Tour de France cyclists burn 8,500 kilocalories: K. R. Westerterp, W. H. Saris, M. van Es, and F. ten Hoor (1986). “Use of the doubly labeled water technique in humans during heavy sustained exercise.” J. App. Physiol. 61 (6): 2162–67.
Triathletes can burn that much energy: B. C. Ruby et al. (2015). “Extreme endurance and the metabolic range of sustained activity is uniquely available for every human not just the elite few.” Comp. Exer. Physiol. 11(1): 1–7.
reportedly ate 12,000 kcal each day: Mun Keat Looi, “How Olympic swimmers can keep eating such insane quantities of food,” Quartz, August 10, 2016, accessed March 21, 2020, https://qz.com/753956/how-olympic-swimmers-can-keep-eating-such-insane-quantities-of-food/.
Alex Hutchinson’s excellent book, Endure: Alex Hutchinson, Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance (William Morrow, 2018).
mental fatigue reduces endurance: See S. Marcora et al. (2018). “The effect of mental fatigue on critical power during cycling exercise.” Eur. J. App. Physiol. 118 (1): 85–92. doi: 10.1007/s00421-017-3747-1.
type of fuel your body burns during exercise: J. A. Romijn et al. (1993). “Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration.” Am. J. Physiol. 265: E380–91.
eating your dogs one by one: Mike Dash, “The most terrible polar exploration ever: Douglas Mawson’s Antarctic journey,” Smithsonian, January 27, 2012, accessed March 21, 2020, https://www.smithsonianmag.com/history/the-most-terrible-polar-exploration-ever-douglas-mawsons-antarctic-journey-82192685/.
averaging an incredible 6,200 kcal per day: C. Thurber et al. (2019). “Extreme events reveal an alimentary limit on sustained maximal human energy expenditure.” Science Advances 5 (6): eaaw0341. doi: 10.1126/sciadv.aaw0341.
showing up in the AEE component: See, for example: H. Pontzer et al. (2016). “Constrained total energy expenditure and metabolic adaptation to physical activity in adult humans.” Curr. Biol. 26 (3): 410–17. doi: 10.1016/j.cub.2015.12.046; S. S. Urlacher et al. (2019). “Constraint and trade-offs regulate energy expenditure during childhood.” Science Advances 5 (12): eaax1065. doi: 10.1126/sciadv.aax1065.
non-exercise activity thermogenesis, or NEAT: J. A. Levine (2002). “Non-exercise activity thermogenesis (NEAT).” Best Pract. Res. Clin. Endocrinol. Metab. 16 (4): 679–702.
studies measuring the NEAT response to exercise: E. L. Melanson (2017). “The effect of exercise on non-exercise physical activity and sedentary behavior in adults.” Obes. Rev. 18: 40–49. doi: 10.1111/obr.12507.
a daily roller-coaster trajectory: K.-M. Zitting et al. (2018). “Human resting energy expenditure varies with circadian phase.” Curr. Biol. 28 (22): 3685–90.e3. doi: 10.1016/j.cub.2018.10.005.
he shaved mouse mothers with nursing pups: E. Król, M. Murphy, and J. R. Speakman (2007). “Limits to sustained energy intake. X. Effects of fur removal on reproductive performance in laboratory mice.” J. Exp. Biol. 210 (23): 4233–43.
injecting intravenous doses of lipids and glucose: “The Dutch Doping Scandal—Part 3,” Cycling News, November 29, 1977, accessed March 21, 2020, http://autobus.cyclingnews.com/results/archives/nov97/nov29a.html [inactive].
mom is being pushed to the brink: H. M. Dunsworth et al. (2012). “Metabolic hypothesis for human altriciality.” PNAS 109 (38): 15212–16. doi: 10.1073/pnas.1205282109.
affecting this metabolic trigger: J. C. K. Wells, J. M. DeSilva, and J. T. Stock (2012). “The obstetric dilemma: an ancient game of Russian roulette, or a variable dilemma sensitive to ecology?” Am. J. Phys. Anthropol. 149 (55): 40–71. doi: 10.1002/ajpa.22160.
12,000 kcal per day figure floating around: Curtis Charles, “Michael Phelps reveals his 12,000-calorie diet was a myth, but he still ate so much food,” USA Today, June 16, 2017, accessed March 21, 2020, https://ftw.usatoday.com/2017/06/michael-phelps-diet-12000-calories-myth-but-still-ate-8000-to-10000-quote.
Katie Ledecky, another star Olympic swimmer: Sabrina Marques, “Here’s how many calories Olympic swimmer Katie Ledecky eats in a day. It’s not your typical 19-year-old’s diet,” Spooniversity, accessed March 21, 2020, https://spoonuniversity.com/lifestyle/this-is-what-olympic-swimmer-katie-ledecky-s-diet-is-like.
Michael Phelps is a large guy, well above average: Ishan Daftardar, “Scientific analysis of Michael Phelps’s body structure,” Science ABC, July 2, 2015, March 21, 2020, https://www.scienceabc.com/sports/michael-phelps-height-arms-torso-arm-span-feet-swimming.html.
the earliest avian ancestors as insulation: M. J. Benton et al. (2019). “The early origin of feathers.” Trends in Ecology & Evolution 34 (9): 856–69.
human ancestors began walking on two legs: Charles Darwin, The Descent of Man: And Selection in Relation to Sex (J. Murray, 1871).
the French Academy famously banned any discussion: S. Számadó and E. Szathmáry (2004). “Language evolution.” PLoS Biology 2 (10): e346. doi: 10.1371/journal.pbio.0020346.
for any trip longer than a mile: Y. Yang and A. V. Diez-Roux (2012). “Walking distance by trip purpose and population subgroups.” Am. J. Prev. Med. 43 (1): 11–19. doi: 10.1016/j.amepre.2012.03.015.
over five million kilocalories worth of jet fuel: A Boeing 747 on an 8,800 mile flight burns 6,000 kilowatt hours per passenger: David J. C. MacKay, Sustainable Energy: Without the Hot Air (UIT Cambridge Ltd, 2009), https://www.withouthotair.com/c5/page_35.shtml.
existential crises: obesity and climate change: “Syndemics: Health in context.” Lancet 389 (10072): 881.
discovery of fossil remains from an extinct hominin: L. S. B. Leakey, P. V. Tobias, and J. R. Napier (1964). “A new species of the genus Homo from Olduvai Gorge.” Nature 202: 7–9.
Discoveries over the subsequent decades: Glenn C. Conroy and Herman Pontzer, Reconstructing Human Origins: A Modern Synthesis, 3rd ed. (W. W. Norton, 2012).
the force with which they pull the bowstring: H. Pontzer et al. (2017). “Mechanics of archery among Hadza hunter-gatherers.” J. Archaeol. Sci. 16: 57–64. doi: 10.1016/j.jasrep.2017.09.025.
Homo erectus, over a million years ago: F. Berna et al. (2012). “Acheulean fire at Wonderwerk Cave.” PNAS 109 (20): E1215–20. doi: 10.1073/pnas.1117620109.
puts the date at around 400,000 years ago: W. Roebroeks and P. Villa (2011). “On the earliest evidence for habitual use of fire in Europe.” PNAS 108 (13): 5209–14. doi: 10.1073/pnas.1018116108.
his excellent book Catching Fire: Richard Wrangham, Catching Fire: How Cooking Made Us Human (Basic Books, 2010).
Wood fires release about 1,600 kcal per pound of fuel: Wikipedia, accessed March 22, 2020, https://en.wikipedia.org/wiki/Wood_fuel.
men and women following raw food diets: C. Koebnick, C. Strassner, I. Hoffmann, and C. Leitzmann (1999). “Consequences of a long-term raw food diet on body weight and menstruation: Results of a questionnaire survey.” Ann. Nutr. Metab. 43: 69–79.
Fires could be used to change the landscape: D. W. Bird, R. Bliege Bird, and B. F. Codding (2016). “Pyrodiversity and the anthropocene: The role of fire in the broad spectrum revolution.” Evol. Anthropol. 25: 105–16. doi: 10.1002/evan.21482; F. Scherjon, C. Bakels, K. MacDonald, and W. Roebroeks (2015). “Burning the land: An ethnographic study of off-site fire use by current and historically documented foragers and implications for the interpretation of past fire practices in the landscape.” Curr. Anthropol. 56 (3): 299–326.
learned to use kilns to made bitumen: P. R. B. Kozowyk et al. (2017). “Experimental methods for the Palaeolithic dry distillation of birch bark: Implications for the origin and development of Neandertal adhesive technology.” Sci. Rep. 7: 8033. doi: 10.1038/s41598-017-08106-7.
building fires hot enough to fire pottery: Cristian Violatti, “Pottery in Antiquity,” Ancient History Encyclopedia, September 13, 2014, accessed March 22, 2020, https://www.ancient.eu/pottery/.
smelt ore to make copper and other metals: “Smelting,” Wikipedia, accessed March 22, 2020, https://en.wikipedia.org/wiki/Smelting.
figured out how to make iron and glass: “History of Glass,” Wikipedia, accessed March 22, 2020, https://en.wikipedia.org/wiki/History_of_glass.
converge on a game-changing insight: J. Diamond and P. Bellwood (2003). “Farmers and their languages: The first expansions.” Science 300 (5619): 597–603.
a horse can comfortably produce around 640 kcal of work: R. D. Stevenson and R. J. Wassersug (1993). “Horsepower from a horse.” Nature 364: 6434.
She could do the work of ten men: Eugene A. Avallone et al, Marks’ Standard Handbook for Mechanical Engineers, 11th ed. (McGraw-Hill, 2007).
On horseback, she could easily cover thirty miles in a day: Nicky Ellis, “How far can a horse travel in a day?” Horses & Foals, April 15, 2019, accessed March 22, 2020, https://horsesandfoals.com/how-far-can-a-horse-travel-in-a-day/.
fertility rates accelerated: J.-P. Bocquet-Appel (2011). “When the world’s population took off: The springboard of the Neolithic demographic transition.” Science 333 (6042): 560–61. doi: 10.1126/science.1208880.
A typical Hadza woman will have six children: N. G. Blurton Jones et al. (1992). “Demography of the Hadza, an increasing and high density population of savanna foragers.” Am. J. Phys. Anthropol. 89 (2): 159–81.
a Tsimane woman, with the caloric benefits: M. Gurven et al. (2017). “The Tsimane Health and Life History Project: Integrating anthropology and biomedicine.” Evol. Anthropol. 26 (2): 54–73. doi: 10.1002/evan.21515.
calls the collective brain: M. Muthukrishna and J. Henrich (2016). “Innovation in the collective brain.” Phil. Trans. R. Soc. B 371: 20150192. doi: /10.1098/rstb.2015.0192.
how to harness the power of the wind to sail: Oldest evidence for sailing is from around 7,500 years ago in the Persian Gulf; see R. Carter (2006). “Boat remains and maritime trade in the Persian Gulf during the sixth and fifth millennia BC.” Antiquity 80 (3071): 52–63. Also see “Ancient Maritime History,” Wikipedia, accessed March 22, 2020, https://en.wikipedia.org/wiki/Ancient_maritime_history.
harness the energy of a flowing river: “Watermill,” Wikipedia, accessed March 22, 2020, https://en.wikipedia.org/wiki/Watermill.
Windmills joined them a few centuries later: “Windmill,” Wikipedia, accessed March 22, 2020, https://en.wikipedia.org/wiki/Windmill.
fossil fuels combine to provide over 35,000 kcal of energy: Energy data: “World Energy Balances 2019,” International Energy Agency, accessed March 23, 2020, https://www.iea.org/data-and-statistics; Population data: “World Population Prospects 2017,” United Nations, Department of Economic and Social Affairs, Population Division, 2017—Data Booklet (ST/ESA/SER.A/401), accessed April 28, 2020, https://population.un.org/wpp/Publications/Files/WPP2017_DataBooklet.pdf.
farmers made up 69 percent of the American workforce: U.S. Census Bureau, Historical Statistics of the United States 1780–1945 (1949), 74, accessed March 23, 2020, https://www2.census.gov/prod2/statcomp/documents/HistoricalStatisticsoftheUnitedStates1789-1945.pdf.
farmers and ranchers make up only 1.3 percent: 2.6 million farmers in 2018: “Ag and Food Sectors and the Economy,” USDA Economic Research Service, March 3, 2020, accessed March 23, 2020, https://www.ers.usda.gov/data-products/ag-and-food-statistics-charting-the-essentials/ag-and-food-sectors-and-the-economy/; the U.S. population in 2018 was 327 million: U.S. and World Population Clock, accessed March 23, 2020, https://www.census.gov/popclock/.
consumes roughly 500 trillion kilocalories each year: Randy Schnepf, Energy Use in Agriculture: Background and Issues, Congressional Research Service Report for Congress, November 19, 2004, accessed March 23, 2020, https://nationalaglawcenter.org/wp-content/uploads/assets/crs/RL32677.pdf.
Hadza adults acquire roughly 1,000 to 1,500 kcal per hour of foraging: Hadza and Tsimane rates of food energy acquisition (Figure 9.2) calculated from production and activity data: Frank W. Marlowe, The Hadza: Hunter-Gatherers of Tanzania (Univ. of California Press, 2010); M. Gurven et al. (2013) “Physical activity and modernization among Bolivian Amerindians.” PloS One 8 (1): e55679. doi: 10.1371/journal.pone.0055679.
a manufacturing job could buy you more than 3,000 kcal: E. L. Chao, and K. P. Utgoff, 100 Years of U.S. Consumer Spending: Data for the Nation, New York City, and Boston, U.S. Department of Labor, 2006, accessed March 23, 2020, https://www.bls.gov/opub/100-years-of-u-s-consumer-spending.pdf.
Sugar was a luxury item: Anup Shah, “Sugar,” Global Issues, April 25, 2003, accessed March 23, 2020, https://www.globalissues.org/article/239/sugar.
the most calories per gram are also the cheapest: A. Drewnowski and S. E. Specter (2004). “Poverty and obesity: The role of energy density and energy costs.” Am. J. Clin. Nutr. 79 (1): 6–16.
beet sugar and high-fructose corn syrup: S. A. Bowman et al., “Retail food commodity intakes: Mean amounts of retail commodities per individual, 2007–08,” USDA, Agricultural Research Service, Beltsville, MD, and USDA, Economic Research Service, Washington, D.C., 2013.
The energy density of an industrialized diet: H. Pontzer, B. M. Wood, D. A. Raichlen (2018). “Hunter-gatherers as models in public health.” Obes. Rev. 19 (Suppl 1):24–35.
time between births: C. E. Copen, M. E. Thoma, and S. Kirmeyer (2015). “Interpregnancy intervals in the United States: Data from the birth certificate and the National Survey of Family Growth.” National Vital Statistics Reports 64 (3).
half a year shorter than we see among the Tsimane: A. D. Blackwell et al. “Helminth infection, fecundity, and age of first pregnancy in women.” Science 350 (6263): 970–72. doi: 10.1126/science.aac7902.
cultural and biological factors behind this change: O. Galor (2012). “The demographic transition: Causes and consequences.” Cliometrica 6 (1): 1–28. doi: 10.1007/s11698-011-0062-7.
40 calories of food for every calorie they spend foraging: H. Pontzer (2012). “Relating ranging ecology, limb length, and locomotor economy in terrestrial animals.” Journal of Theoretical Biology 296: 6–12. doi:10.1016/j.jtbi.2011.11.018.
we burn 8 calories for every calorie of food we produce: “U.S. Food System Factsheet,” Center for Sustainable Systems, University of Michigan, 2019. http://css.umich.edu/sites/default/files/Food%20System_CSS01-06_e2019.pdf [inactive].
we consume a staggering 25 quadrillion kilocalories: “U.S. energy facts explained,” U.S. Energy Information Administration, accessed March 23, 2020, https://www.eia.gov/energyexplained/us-energy-facts/.
In a few countries, per capita energy consumption: Data and Statistics, “Total primary energy supply (TPES) by source, World 1990–2017,” International Energy Agency, 2019, accessed March 23, 2020, https://www.iea.org/data-and-statistics.
we’ve got around fifty years’ worth of oil and natural gas: Hannah Ritchie and Max Roser, “Fossil Fuels,” Our World in Data, 2020, https://ourworldindata.org/fossil-fuels.
the Earth 0.8°C (1.4°F) warmer than it was in the late 1800s: National Academy of Sciences, Climate Change: Evidence and Causes (National Academies Press, 2014). doi: 10.17226/18730.
an additional 8°C warming globally: R. Winkelmann et al. (2015). “Combustion of available fossil fuel resources sufficient to eliminate the Antarctic ice sheet.” Science Advances 1 (8): e1500589. doi: 10.1126/sciadv.1500589; K. Tokarska et al. (2016). “The climate response to five trillion tonnes of carbon.” Nature Clim. Change 6: 851–55. doi: 10.1038/nclimate3036.
during the Paleocene-Eocene Thermal Maximum: J. P. Kennett and L. D. Stott, “Terminal Paleocene Mass Extinction in the Deep Sea: Association with Global Warming,” ch. 5 in National Research Council (US) Panel, Effects of Past Global Change on Life (National Academies Press, 1995). https://www.ncbi.nlm.nih.gov/books/NBK231944/.
at least a hundred meters (328 feet) higher than today: B. U. Haq, J. Hardenbol, and P. R. Vail (1987). “Chronology of fluctuating sea levels since the Triassic.” Science 235 (4793): 1156–67.
the largest cities, are less than ten meters above sea level: G. McGranahan, D. Balk, and B. Anderson (2007). “The rising tide: Assessing the risks of climate change and human settlements in low elevation coastal zones.” Environment and Urbanization 19 (1): 17–37. doi: 10.1177/0956247807076960.
half of us live less than a hundred meters above sea level: J. E. Cohen and C. Small (1998). “Hypsographic demography: The distribution of human population by altitude.” PNAS 95 (24): 14009–14. doi: 10.1073/pnas.95.24.14009.
steadily, if slowly, declining since the 1970s: Hannah Ritchie and Max Roser, “Energy,” Our World in Data, 2020, accessed March 23, 2020, https://ourworldindata.org/energy.
Work commutes in the United States and Europe: U.S.: Elizabeth Kneebone and Natalie Holmes, “The growing distance between people and jobs in metropolitan America,” Brookings Institute, 2015, https://www.brookings.edu/wp-content/uploads/2016/07/Srvy_JobsProximity.pdf; Europe: “More than 20% of Europeans Commute at Least 90 Minutes Daily,” sdworx, September 20, 2018, accessed March 23, 2020, https://www.sdworx.com/en/press/2018/2018-09-20-more-than-20percent-of-europeans-commute-at-least-90-minutes-daily.
we need to get to zero carbon emissions globally by 2050: R. Eisenberg, H. B. Gray, and G. W. Crabtree (2019). “Addressing the challenge of carbon-free energy.” PNAS 201821674. doi: 10.1073/pnas.1821674116.
there are several plausible strategies: David Roberts, “Is 100% renewable energy realistic? Here’s what we know,” Vox, February 7, 2018, accessed March 23, 2020, https://www.vox.com/energy-and-environment/2017/4/7/15159034/100-renewable-energy-studies.
fossil fuels kill thousands more people: A. Markandya and P. Wilkinson (2007). “Electricity generation and health.” Lancet 370 (9591): 979–90.
processed foods lead to overeating and weight gain: K. D. Hall et al. (2019). “Ultra-processed diets cause excess calorie intake and weight gain: An inpatient randomized controlled trial of ad libitum food intake.” Cell Metabolism 30(1): 67–77.e3. doi:10.1016/j.cmet.2019.05.008.
Double Chocolate Dunkin’ Donut holds 350 kilocalories: Dunkin’ Donuts, accessed March 23, 2020, https://www.dunkindonuts.com/.
Taxes on soda and other sugar-sweetened beverages: A. M. Teng et al. (2019). “Impact of sugar-sweetened beverage taxes on purchases and dietary intake: Systematic review and meta-analysis.” Obes. Rev. 20 (9): 1187–1204. doi: 10.1111/obr.12868.
Americans with low incomes lived in food deserts: “Food Access Research Atlas,” USDA Economic Research Service, accessed March 23, 2020, https://www.ers.usda.gov/data-products/food-access-research-atlas.
cheaper per kilocalorie than fresh fruit and vegetables: A. Drewnowski and S. E. Specter (2004). “Poverty and obesity: The role of energy density and energy costs.” Am. J. Clin. Nutr. 79 (1): 6–16.
billions of dollars in subsidies each year: Kimberly Amadeo, “Government Subsidies (Farm, Oil, Export, Etc): What Are the Major Federal Government Subsidies?” The Balance, January 16, 2020, accessed March 23, 2020, https://www.thebalance.com/government-subsidies-definition-farm-oil-export-etc-3305788.
As Stephan Guyenet and others have argued: Stephan Guyenet, The Hungry Brain: Outsmarting the Instincts That Make Us Overeat (Flatiron Books, 2017).
has tripled, from roughly 25 percent in 1910: I. D. Wyatt and D. E. Hecker (2006). “Occupational changes during the 20th century.” Monthly Labor Review 129 (3): 35–57.
13 percent of all jobs in the U.S. are classified as “sedentary”: “Physical strength required for jobs in different occupations in 2016 on the Internet,” The Economics Daily, Bureau of Labor Statistics, U.S. Department of Labor, accessed March 23, 2020, https://www.bls.gov/opub/ted/2017/physical-strength-required-for-jobs-in-different-occupations-in-2016.htm.
increasing daily physical activity and reducing disease: D. Rojas-Rueda et al. (2016). “Health impacts of active transportation in Europe.” PloS One 11 (3): e0149990. doi: 10.1371/journal.pone.0149990.
People living in poverty suffer from higher rates of obesity: O. Egen et al. (2017). “Health and social conditions of the poorest versus wealthiest counties in the United States.” Am. J. Public Health 107 (1): 130–35. doi: 10.2105/AJPH.2016.303515.
marginalized communities have worse health: J. R. Speakman and S. Heidari-Bakavoli (2016). “Type 2 diabetes, but not obesity, prevalence is positively associated with ambient temperature.” Sci. Rep. 6: 30409. doi: 10.1038/srep30409; J. Wassink et al. (2017) “Beyond race/ethnicity: Skin color and cardiometabolic health among blacks and Hispanics in the United States.” J. Immigrant Minority Health 19 (5): 1018–26. doi: 10.1007/s10903-016-0495-y.
Loneliness has become so prevalent: N. Xia and H. Li (2018). “Loneliness, social isolation, and cardiovascular health.” Antioxidants & Redox Signaling 28 (9): 837–51. doi: 10.1089/ars.2017.7312.
Time outside can relieve stress: K. M. M. Beyer et al. (2018). “Time spent outdoors, activity levels, and chronic disease among American adults.” J. Behav. Med. 41 (4): 494–503. doi: 10.1007/s10865-018-9911-1.
typical American spends 87 percent of his life in buildings: N. E. Klepeis et al. (2001). “The National Human Activity Pattern Survey (NHAPS): A resource for assessing exposure to environmental pollutants.” J. Expo. Anal. Environ. Epidemiol. 11 (3): 231–52. https://www.nature.com/articles/7500165.pdf?origin=ppub