Exercise—The Other Half of the Antidote
Britt is a depressed thirteen-year-old boy who weighs 230 pounds and is getting bad grades, in part due to excessive “screen time.” His fifteen-year-old brother is 320 pounds and has no intention of altering his lifestyle. Britt sees the misery of his brother and uses him as a “negative role model.” Over the next three years, as puberty progresses, Britt starts wrestling in high school, practicing three to four hours a day. He slims down without appreciably altering his diet and without shedding any pounds. He grows into his weight and places second in the state for his weight class. By age eighteen, his depression has lifted, his academics have improved, and he is valedictorian of his high school class.
Jack LaLanne passed away in January 2011 at the ripe old age of ninety-six. The “father” of modern exercise, he adopted a healthy lifestyle at age fifteen and practiced what he preached until the day before his death. He had it right: exercise is the key to optimal health. But not everyone benefits equally. Jim Fixx, one of the pioneer American runners and the author of The Complete Book of Running, bit the bullet at age fifty-two. Maybe Fixx died for his first thirty-five years of bad lifestyle choices: before he took up running he smoked two packs per day and weighed 240 pounds. How about Arthur Ashe? The premier tennis player had a heart attack at age thirty-six. Maybe exercise can’t reverse a lifetime of indiscretion. Maybe genetic factors play a role. Or maybe exercise has different benefits in different people.
Either way, expecting that exercise will let you live longer is very different from expecting that exercise can help you lose weight. LaLanne didn’t gain a pound all those years on TV. That was because he ate properly. Don’t get me wrong; there’s nothing bad about exercise (although it may not provide all the effects you expect). Exercise is the single best thing you can do for yourself. It’s way more important than dieting, and easier to do. Exercise works at so many levels—except one: your weight.
The Myth of Exercise
If “a calorie is a calorie” and one ingested equals one burned, then exercise should cause weight loss, and doing a lot of exercise, even if you keep eating the same foods, should make you shed some serious poundage. But it doesn’t. The calories you eat or drink may have a positive effect on your weight, but the energy you burn doesn’t do the opposite. There is not one study that demonstrates that exercise alone causes significant weight loss, and a meta-analysis (designed to assess significance over many studies at once) proved it; moderate exercise resulted in a weight loss of 2.2 pounds and vigorous exercise in a loss of 3.5 pounds.1 Given our current obesity epidemic, that just ain’t gonna cut it. As an example, a friend of mine decided to clear her post-baby “muffin top” by initiating a moderate-to-vigorous exercise program. Twelve weeks later, she was up five pounds. She felt better, but her muffin top hadn’t changed. She asked me what she was doing wrong. Nothing, I told her. She was doing just fine and was likely much healthier than at the outset. Her waist would be smaller, but the muffin top was subcutaneous fat; she could still “pinch the inch.” She got into her pre-pregnancy jeans anyway.
Burning a pound of fat liberates 2,500 calories, so it had always been assumed that you can lose one pound by eating 2,500 calories less or exercising 2,500 calories more. However, a recent scientific analysis2 shows the fallacy of expecting increased energy expenditure to promote weight loss. As people lost weight, their energy intake had to drop even further to keep the weight loss going. On average, obese people had to eat 3,977 calories less to burn off that one pound of fat. So you can see that trying to burn weight off with exercise is extremely difficult, if not downright impossible. A second reason that exercise doesn’t cause weight loss is that when you exercise, you build muscle. That’s good for your health, but it doesn’t reduce your weight.
If chapters 4–9 say anything, it’s that studying an event as complex as obesity means looking at the entire gamut of behaviors—because, in the real world, none of them occur in isolation, and all of them are driven by biochemistry. Guaranteed, if you hold food intake constant and then institute vigorous activity, some weight loss will follow, but not much. That’s why every exercise plan promotes good nutrition. And that’s why so many weight-loss programs want to sell you their food. But it’s the biochemistry that drives the behavior.
Oh, you say to me, I know people who joined the armed forces and they lost a lot of weight. Wrestlers do it all the time. NFL linemen show up in training camp overweight and out of shape and by the end of exhibition season they’re back at playing weight. This is the fact that perpetuates the myth. Anyone can lose weight if his or her environment is changed. “Boot camp” is a secluded and controlled environment. Every aspect of your daily regimen, from food to exercise to sleep, is regulated. The trick is to change behavior while in your routine environment. Don’t bet the ranch. As we learned in chapter 4, behavior is a result of biochemistry, and biochemistry is a result of environment. Even the contestants on The Biggest Loser get a personal trainer and a chef to control their environment. But in a free-range situation, in which the general populace finds itself, energy intake will rise to meet energy expenditure to maintain the same level of adiposity. And in the majority of obese people, we know why: leptin…again.
Energy Expenditure in a Nutshell
To explain energy expenditure, we’re going to assume a 2,000-calorie intake and 2,000-calorie output for an average person. This value comes both from observation and from the Harris-Benedict equation, a guesstimate used by dietitians to generate dietary plans for individual patients.
Everyone equates energy expenditure with exercise. Your aerobics instructor will yell at you, “Feel the burn.” Burning it means burning it. In point of fact, physical activity is the minority of energy expenditure, accounting for anywhere from 5 percent (the ultimate couch potato, at about 100 calories) to 35 percent (the gym rat, at about 700 calories) of total energy expenditure based on the level and degree of activity. While physical activity may not account for the largest percentage of energy expenditure, it is the only component that will improve your health—and the more you do, the better.
There are two other components. It might seem hard to believe, but the largest percentage of your calories is burned while sleeping and watching TV (but this does not mean that you should increase your hours on Facebook or World of Warcraft). Resting energy expenditure (REE, the energy you burn lying on the couch) accounts for about 60 percent (or 1,200 calories per day) of total energy expenditure, is dependent on your size, and is usually excluded from concern. Lastly, a process called the thermic effect of food (TEF, the energy you burn to absorb, digest, and metabolize the food you eat) accounts for about 10 percent (or 200 calories). While it’s true that for the most part REE and TEF are not easy to change in most people, it should be noted that some patients with obesity exhibit problems with each. And there are some tricks to increase REE and, to a lesser extent, TEF (see chapter 18).
Resting Energy Expenditure
Rudy Leibel at Columbia University in 2004 was quoted as saying, “Obese people tell me all the time they eat very little, they eat like a bird…well, maybe a pterodactyl.” Yet Rudy himself showed that in response to weight loss, REE declines commensurate with the number of pounds lost, working to keep your weight stable.3 Don’t blame your exercise regimen; blame your biochemistry. While you’re burning more energy by going to that Zumba class, your REE is going to thwart you by evening out your overall percentage. Fat cells want to remain filled; they aren’t going away without a fight. In response to a decline in either leptin synthesis or leptin signaling (which the hypothalamus interprets as starvation), REE is reduced from 50 calories per kilogram fat-free mass to 42 calories per kilogram fat-free mass, or an improvement in energy efficiency of 16 percent, resulting in a decrease of total energy expenditure of 0.16 x 0.65, or 10 percent. Assuming that standard adult 2,000-calorie intake, that’s a decrease of 200 calories, which easily rivals the increase in caloric intake that has been observed in the past thirty years.
Furthermore, there are patients that have specific reductions in REE as part of their general pathology. As REE accounts for the majority of energy expenditure, this is the greatest predictor of weight gain. Children with certain forms of developmental delay are born with lack of muscle tone (called hypotonia) and are “floppy” at birth. Children with various forms of mitochondrial dysfunction (e.g., Prader-Willi syndrome)4 burn energy at rest about 60–70 percent of normal. This means they need fewer calories. But that means a lower leptin, and their brain feels starved, jacking up the caloric intake.
Thermic Effect of Food (TEF)
You have to put energy in to get energy out. Chewing, moving food through the GI tract, absorbing, and processing food will burn some energy. TEF usually accounts for 10 percent (or 200 calories per day) of all energy burned. Many obese children are not hungry when they awaken (in part because many of them had a big snack or meal just before bedtime), so their body’s degree of energy burning is not ratcheted up prior to their departure for school. This is one reason, among many, that eating breakfast is important for prevention and treatment of obesity, especially in children (see chapter 18). Not eating breakfast has many other disadvantages. It means not performing well on tasks because of distraction due to lack of food. Not eating breakfast means the stomach hormone ghrelin, which conveys the signal for hunger, is not suppressed throughout the morning. Obese people rationalize not eating breakfast by saying that’s one less meal’s worth of calories. That couldn’t be further from the truth. Numerous studies show that people who skip breakfast eat more during the daylight hours, in part because ghrelin rises to high levels. This leads to overconsumption of calories at lunch, dinner, and prior to bedtime, all driving further obesity.
Even though oxidation of fats (see chapter 10) liberates a lot of energy, a little bit of energy is spent making it work. Another way to take advantage of TEF to is to consume some form of protein at breakfast. Burning protein costs more energy than burning other foodstuffs.5 Protein does not stimulate insulin to the same extent as carbohydrates do, and increases satiety better than other nutrients. So consuming some protein at breakfast is a smart and very defensible practice. People who eat veggie omelets at breakfast are way less hungry at lunchtime.6
Physical Activity
Finally, physical activity. You can be completely sedentary, or you can be Olympic swimmer Michael Phelps. The range of energy expenditure by physical activity that humans can achieve is quite remarkable; topped perhaps only by how many calories can be eaten. Phelps eats everything in sight, on the order of 12,000 calories a day. As hard as he works, he doesn’t expend 12,000 calories in physical activity—even marathon runners don’t burn that kind of energy. The Cleveland Clinic Center for Consumer Health estimates that a 130-pound runner will burn 2,224 calories during a marathon, a 165-pound runner will burn 2,822 calories, and a 210-pound runner will burn 3,593 calories. Yet Phelps can eat anything he wants, and he doesn’t gain weight. That’s because exercise increases the number of mitochondria in the form of increased muscle. And increased muscle means you burn more energy at rest. So Michael Phelps has a higher REE than you do. And that’s why exercise is good; because it builds muscle, and muscle burns energy even at rest.
Physical activity is the most misunderstood aspect of obesity medicine. People think if they exercise they will lose weight. That’s a pipe dream. Most of the studies of exercise for obesity in children are free-range community interventions and use either weight or BMI as their outcome. And no amount of exercise is going to change BMI, a measure of body size, because BMI is the wrong outcome. In the absence of environmental control, caloric intake will increase to meet the shortfall. Remember, your subcutaneous fat can actually be good for you. But as discussed in chapter 8, the target of exercise is muscle and bone.
What Exercise Actually Does
So, if you’re not going to lose weight, why go to spin class? Why is exercise so good for you? Diet is about pounds, exercise is about inches. Diet is about weight, exercise is about health. Exercise does the one thing that dietary restriction cannot: it builds muscle. This is a poorly understood concept, because most people, including clinicians, equate BMI with body fat. BMI does not take into account the difference between muscle and fat, or the difference between subcutaneous and visceral fat. Several studies have examined body composition before and after long-term exercise. What they show is that percentage body fat declined. Absolutely true. But it’s because muscle increased. And, in the process, metabolic status improved—both because visceral fat went down (a little) and because muscle went up (a lot) (see chapter 8).
You want to improve your insulin sensitivity—and exercise does just that. It makes you build muscle at the expense of visceral and especially liver fat. But you can’t see this by stepping on a scale. By improving insulin sensitivity and lowering insulin levels, exercise improves leptin signaling, thereby increasing your sympathetic tone (see chapter 4), energy expenditure, and quality of life.
And these metabolic improvements translate into disease prevention. A study of thirty-eight thousand American men showed that physical activity was more potent in preventing heart disease than being normal weight.7 But what about the ultimate outcome: does exercise promote longevity? A recent study out of Taiwan looking at the death rates of over four hundred thousand subjects suggests that moderate-intensity exercise for fifteen minutes a day could increase lifespan by as much as three years, even in patients with known heart disease.8 And they didn’t control for diet; if they had, they would have seen an even greater effect of exercise on longevity. Given that 15 minutes a day accounts for only 91 waking hours a year, or 273 hours in 3 years, a 3-year life extension for 273 hours of exercise performed is a pretty darn good trade.
The Biochemistry of Exercise
Exercise is truly the other half of the antidote. It will not cure obesity, but it goes a long way toward mitigating all its negative effects, especially those of metabolic syndrome (see chapter 9). Biochemically, exercise does three things:
1. Exercise directly activates your sympathetic nervous system (SNS) (see chapter 4). The SNS sends a signal to your muscles to make new mitochondria, which means that more energy (glucose or fatty acids) can be burned. The age of mitochondria plays a big role, because old mitochondria are inefficient, “leaky,” and make more ROS (see chapter 9), which contributes to insulin resistance. Exercise clears away those old mitochondria, allowing for clean, efficient use of energy by muscles.9 This improves muscle insulin sensitivity, which is key to improving your general metabolic health.
2. Exercise is your internal stress reducer. Britt became a well-adjusted teenager (not always an oxymoron) in part because he started to work out. While blood cortisol levels (see chapter 6) rise immediately upon exercise (as they are part of the process that keeps your blood sugar and blood pressure up), they come down quickly, and stay down the rest of the day.10 To reduce your blood pressure, you may want to consider exercise—not because your weight will go down, but because exercising will reduce your stress levels and release endorphins (feel-good chemicals in your brain) to make you feel better throughout the day. This is how runners get their “runner’s high.” We want to keep our cortisol levels low to improve our long-term metabolic status. A little pain, a lot of gain.
3. Perhaps most important, exercise increases the speed of your liver’s Krebs cycle (see chapters 9 and 11) and makes it burn energy cleaner.11 This determines how much energy will be shuttled out of the mitochondria and converted to liver fat. Four factors have been shown to speed up the liver’s Krebs cycle: cold, altitude, the thyroid hormone (we gave extra thyroid hormone to obese women back in the 1960s and it made them crazy), and exercise. Cold and altitude are a potent anti-obesity combination. Take the difference between Switzerland and Germany. Switzerland eats virtually the same diet as does Germany. Fat and carbohydrate together, an obesogenic diet if I ever saw one. Lots of potatoes, lots of bread, lots of cheese, lots of cream sauces, lots of beer. Yum. Their rates of physical activity are also virtually the same. But Switzerland is high, cold, and thin (only 8 percent obesity), while Germany is low, less cold, and fat (16 percent obesity). Same thing in Colorado: you’re so proud because the CDC obesity map shows that you’re the least obese state in the United States. But I know the real reason you’ve lagged behind the rest of the country, and it isn’t your food or your active lifestyle—it’s your geography. So, everyone, if you don’t want to exercise, move to Switzerland or Colorado!
Cardio or Isometric Exercise?
Assuming you’re a mere mortal at sea level and not an Olympian on a mountain, what kind of exercise should you perform to get the health benefits? The standard mantra was that low-intensity, long-interval exercise, otherwise known as “cardio” (e.g., running), worked your heart and provided all the cardiovascular benefits. There were even those who eschewed resistance or isometric exercise because it temporarily reduced the blood flow to the heart, thus slowing it, and because it increased peripheral muscle, it did not promote weight loss. But recent prospective studies show that high-intensity interval training (fits of extreme activity interspersed with low levels of exercise)12 or even strength training (weight lifting)13 provide equal improvements in waist circumference and blood vessel flow. So, don’t sweat what kind of exercise, just sweat!
It’s All Good, Except When It’s Not
Of course, you can overdo exercise. Exercise promotes the release of chemicals called “endogenous opioids,” or “endorphins,” which cause the hypothalamus to reduce the release of the pituitary hormones luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which reduces estrogen production by the ovaries. In women, this leads to the stoppage of menses and long-term reductions in bone mass—not a good thing, given that women are destined to lose bone mass rapidly upon menopause.
When obese patients start to exercise, they may be at significant risk for injury because of the excess weight they are carrying. The obese need to exercise to improve their overall health, but they need to start out slowly, because they are at greater risk for muscle strains and pulls as well as fractures. Studies demonstrate that the fracture rate among the obese is four times higher than the general population.14
And the biggest problem of all: the beneficial effects of exercise, while excellent for your body and your metabolism, are relatively short-lived, and have to be frequent and sustained. Studies demonstrate that levels of PPAR-gamma coactivator 1-alpha (PGC-1α; the protein in muscle cells that turns on all the good muscle metabolic effects and tells the mitochondria to divide) decline within a day of cessation of exercise, and insulin sensitivity returns to baseline within fifteen days.15 So, those of you weekend warriors who think you’re doing yourself some good—it may not be as good as you think. If you’re going to use exercise as your protection against chronic disease, you’ll have to be consistent about it.
Fat and Fit Is Better Than Thin and Sick
Exercise is the other half of the antidote. It is your best defense against metabolic dysfunction. Here’s another way to look at it. Every molecule of energy that you absorb has one of three fates: First, you can burn it, in which case your insulin doesn’t rise, you won’t gain weight, and you won’t do metabolic damage. Second, you can store it, in which case your insulin goes up, you gain weight, and you do some metabolic damage. Or third, the energy goes out in your urine, in which case you wreak complete metabolic havoc and cause kidney damage, as seen in poorly controlled diabetics who end up on dialysis. Burning energy is always preferable to the other two options. Just don’t expect exercise to induce weight loss, unless it is coupled with some sort of dietary intervention as well.
So let’s go back to chapters 1 and 9, where I mentioned that 40 percent of normal-weight individuals are insulin resistant or have metabolic syndrome, and those who do also have fatty livers. Who do you think is better off? The fat person who exercises, or the thin one who watches nonstop Law & Order marathons? Recent studies have demonstrated that fitness mitigates all the negative effects of obesity on visceral fat,16 health complaints,17 and longevity.18 So does the fat and fit person deserve to be discriminated against? As long as she keeps it up, she’ll likely live longer than the stick thin model on the cover of Vogue. Indeed, overweight people with BMIs between 25 and 30 live longer than thin people with BMIs of less than 19.19
The Greatest Disservice, and by the Medical Profession
Nonetheless, doctors continue to promote the party line with their obese patients. The corollary to “a calorie is a calorie” is the mantra “If you’d only exercise, you’d lose weight.” Not only is this wrong, it’s downright detrimental. Patients who monitor their exercise progress on a home scale are destined for disappointment. But their doctors tell them it will work, and the patients trust them. So they think they’re failures, get depressed, and stop exercising and start eating, because they think it’s no use. A great way to make metabolic syndrome even worse. Irrespective of weight, consistent exercise (even just fifteen minutes a day) is the single best way for people to improve their health. That’s 273 hours paid in for 3 years of life gained, or a 64,000 percent return on investment. The best deal in all of medicine.