Before you read this chapter, do us one favor: Take every assumption you have about eating, toss it in the garbage disposal, and grind it up with your apple cores and onion skins. Why? An assumption, in many cases, can be what’s holding you back from changing your diet, changing your health—and in effect, changing your life.
Think about how many assumptions you already make about the timing of meals. That if you eat very little during the day, you can feast at dinner. That the supreme dictator of your health is the number of calories you eat, no matter when you eat them. That having chicken breast for breakfast sounds as wacky as a bare-bellied fan at a December football game in Green Bay.
All those assumptions have come about for a variety of reasons—some through folklore, some through tradition, some through science. But that doesn’t mean they’re always accurate, healthy, or the best for you in the long run. So while you read this chapter, try to suspend your preconceived notions about the timing of eating as we take you through our major guidelines for how to best structure your daily diet.
From Chapter 1, you know the importance of your circadian rhythm and food (something we also call chrononutrition—the idea that food patterns should align with your body’s internal clock for optimum health). Here, we’ll take those big-picture science concepts and put them into action, so you can see the way they work in your daily life. Of course, the tricky part here is that everybody (and every body) is different. Every day is different. Every stressor is different. Every food interaction with your biology can be different.
The key to eating smartly is knowing how to adjust to certain circumstances. After all, that’s the focus of much of this book: learning how to eat in a variety of situations (see Part 3). But here, we want to provide you with a science-based food foundation, so that you can use the When Way style of eating for the majority of your life.
Now, we also know that some of these principles will fly in the face of the way you may eat now. And although change isn’t always easy, what we ask is that you simply give this approach a try for two to three weeks. That will go a long way in helping you form new habits. More importantly, we believe that you will feel better—and that will be the inspiration you need to make these four guidelines the basis of a new way of eating.
GUIDELINE 1: EAT WHEN THE SUN SHINES.
There are a lot of culprits behind the number of health problems Americans face: lack of exercise, lots of fries, food portions the size of beach bungalows. We know that health problems are a complex soup of causes and biological reactions, and part of this book will help you navigate that complexity.
As we tinker with strategic adjustments you can make to nudge your biological systems toward good health, one of the best places to start is to limit the window of time in which you eat. This counteracts the one-two punch of eating at night and eating for a long window during a 24-hour period—that is, feeding from the time you wake until the time you go to sleep.
To best maximize chrononutrition, eat only during daytime, or during an approximate 12-hour window (or shorter) every day.
To the best of your ability, try to align when you eat with when your body is ready to eat. In other words, eat in chorus with your circadian rhythm. Remember, this biology is determined by the light and designed to most efficiently utilize your most scarce resource: energy.
Why do humans have a circadian rhythm? Because your biology evolved to favor the conditions your primitive ancestors lived under. Your ancestors didn’t have electricity (how they managed without Instagram, we’ll never know) so they couldn’t see well at night. That meant their active period was confined to the daylight hours; they rested when the sun set.
Considering that it’s pretty much impossible to eat when you are sleeping (with a few exceptions), your body evolved to be primed for food during the day. Although electricity allows us to extend our day (and it may be more romantic to eat by candlelight), it’s not ideal for our biology. The changing light cycle that trains your circadian rhythm helps set the cycle of your hormones. As evening comes, cortisol starts to drop and melatonin starts to rise as the body prepares for sleep. In addition, your insulin resistance increases throughout the day and is at maximum capacity during the overnight fast. All of which is to say, your body wants you to eat when the sun shines and fast when the sun sets.
Not only does this make sense based on what we know about circadian rhythm, but studies of animals and even a few of people have shown significant benefits to time-restricted feeding, that is, eating only during a limited window. (For any of our South Pole readers—howdy!—this does not apply to those in extreme climates with long days or nights.)
We get some of these insights from work in fruit flies, those pesky little bugs that swarm in your kitchen around ripe fruits and vegetables. Turns out these flies (known by scientists as Drosophila) are often studied to better understand the genetics of cardiac dysfunction; humans actually have more in common with these little guys when it comes to the development of the heart than you might think.
When aging fruit flies are allowed constant access to their favorite laboratory chow, they sleep less, don’t fly as well, and have more variability in their weight; their hearts don’t work as well. But when scientists allow them access to food for only 12 hours a day instead of 24, there’s a dramatic difference. Older flies sleep more like babies, their weight remains constant, their flight improves, and their heart function remains stable.1
We see similar patterns in mice. When they’re fed around the clock with a high-fat diet, they gain a significant amount of weight and develop markers for metabolic syndrome (like high blood pressure, high blood sugar, and low healthy HDL cholesterol). But when scientists restrict the time they have access to the high-fat diet to an eight-hour window during their active period, something dramatic happens: The mice eat the same number of calories but do not become obese or develop insulin resistance, fatty liver, or as much inflammation.2
The studies of humans don’t have enough data to make definitive statements, but they do yield interesting findings. One study from a group at the Salk Institute in La Jolla, California, found that when people reduced their total feeding time from 14 hours a day to 11 hours, they were able to lose weight, have more energy, and sleep better after just 16 weeks.3
What to Do Now: Try to eat your daily calories while the sun shines within a 12-hour window for three days. That means no night eating (if you find yourself in a nutritional emergency, reach for some crunchy raw vegetables). If you can make it three days, try for a week. Ideally, we’d like to see you work up to three weeks in a row. But if you need to adjust, try eating this way five days a week, allowing yourself more flexibility.
GUIDELINE 2: EAT MORE IN THE MORNING AND LESS LATER ON.
If your day starts like ours, it’s probably a tornado of to-dos: shower, brush teeth and hair, shave face and/or legs, get the household going, check your phone 437 times before you get in the car, and get rocking. If you’re lucky, you’ll cram some kind of breakfast bar down your gullet and get on with your day. Or maybe you’ll just skip that part, instead ingesting a gallon of coffee and grabbing some grub for lunch.
About 25 percent of people almost never eat breakfast.4 Guess what: The two of us used to fall into that category, too. Indeed, the “breakfast is the most important meal” doctrine had been shoved down our throats for years. But we just didn’t eat it all that often because we weren’t hungry in the morning (maybe because we ate so much at night). As with many of you, the demands of the day distracted us.
After reviewing all of the research, we’ve changed our minds—and our habits.
The When Way of eating tells us that we should front-load our day with food. But that doesn’t mean you have to do it at breakfast. The key: Breakfast and lunch seem to be the most important meals—not necessarily one or the other.
Breakfast didn’t always have the nutritionally regal status it’s ascribed today. In fact, according to culinary historians, eating it was tantamount to committing a sin during the early Middle Ages.5 (According to us, it’s still a sin if breakfast involves the words “Froot” and “Loops.”) But as the centuries passed and tastier culinary options like coffee and chocolate were discovered, the meal gained more universal acceptance. Some say Seventh-Day Adventist preacher James Caleb Jackson and doctor John Harvey Kellogg, who in the late 19th century invented what would become our modern-day cereal, cemented breakfast’s role as a necessity for health into the cultural consciousness.6
Today, numerous studies support the importance of eating breakfast for health and find that people who skip it have worse nutrition,7 increased risk of type 2 diabetes,8 more hypertension,9 more coronary heart disease,10 greater obesity,11 and higher risk of metabolic syndrome12 than people who do eat breakfast.
And that’s where the directive comes from: For optimum health, you must eat breakfast. So case closed, right? Not so fast.
The studies cited are observational, which means they cannot prove cause and effect in the way the gold-standard randomized clinical control trial can. So although there is an association between eating breakfast and decreasing all those health risks, that doesn’t mean that breakfast is the reason why. In other words, no one has proved that breakfast or lack thereof is the cause. (To complicate matters further, there is a lot of bias among people who do research on how great breakfast is for health—and often, researchers are more likely to draw stronger conclusions than their research findings actually support.)
So what’s an oatmeal lover to do?
Studies of circadian rhythms show that our peak hunger occurs at night (around 8 p.m.), but that our body is actually primed to interact with food in the healthiest way in the morning. That’s the central conflict at the core of what makes eating healthy so difficult. Our stomach wants one thing, but our biology wants another.
In the morning, our bodies are the least insulin resistant and our microbiome is ready for a meal. But as the day goes on, our cells become more resistant to insulin, which isn’t good for our health. So, yes, it’s better to eat early. But it’s not just about one meal; it’s about how you eat throughout the entire day.
The case for eating breakfast: It turns out that there are actually a few gold-standard randomized trials that examine how eating versus skipping breakfast affects weight. The best trial, conducted at Vanderbilt University in 1992, gathered people who normally ate breakfast, as well as people who normally skipped breakfast, and randomly assigned them to keep up their normal habits or switch teams. The study found breakfast had no effect on weight loss, except that people who ate it were less likely to snack and ate less fat throughout the day.13 Other trials also found no difference in weight but determined other health benefits of eating breakfast. In one study, the people assigned to skip the meal ended up with higher LDL (bad) cholesterol;14 another found that people with type 2 diabetes who skipped breakfast had higher blood sugar after lunch and dinner, compared with when they didn’t skip the meal.15 Many other studies have shown that blood sugar rises or is inconsistent (which is bad for your health as well) throughout the day in people who skip breakfast.16,17,18
The case for less late eating: Not eating breakfast also means that you may eat more later in the day—and that has disadvantages. One study found that eating after 8 p.m. was associated with an increased risk of obesity.19 Another study followed more than 1,200 people for six years and found that those who ate a larger percentage of their total daily calories at night had a much greater risk of developing obesity, metabolic syndrome, and a fatty liver compared with those who ate a smaller percentage of their total daily calories at that time.20
Eating early versus eating late: An important study examined the effect of meal timing on a low-calorie diet plan for women who were overweight. Women were assigned to either eat the largest proportion of their calories early in the day (at breakfast) or late in the day (at dinner). The women who had consumed more of their calories for breakfast lost more weight and inches off their belly by the end of the 12-week study. Fasting glucose, insulin, and a hunger hormone called ghrelin were reduced most in the group that ate early compared with the group that ate late. Triglyceride levels decreased in the early-eating group but increased in the late-eating group. That’s all good for early eaters.21
More support for eating most of your calories earlier was found in a study conducted in Spain, where lunch is typically the largest meal of the day. Researchers compared people on a 20-week diet plan who ate their lunch before or after 2 p.m. Even though both groups ate about the same amount of calories, those eating a late lunch were more likely to have a smaller or no breakfast than those eating an early lunch; they also lost less weight and lost it more slowly than those who ate the early lunch.22
What to Do Now: Whether it’s the most important meal or not, the evidence is clear that breakfast should either be your largest meal of the day or your second largest. But we get it. Sometimes, you don’t have a lot of time in the morning. If that’s the case, make lunch your largest meal. Together, aim to get three-quarters of your daily calories before 2 p.m., between breakfast and lunch. Snacks and dinner should make up about a quarter of the day’s calories. In terms of your macros, breakfast should be made up of complex carbohydrates (not sugar), protein, and fat (unsaturated, please). Adding protein to breakfast reduces appetite and food intake later in the day. In fact, a small study even suggests that the satiating effect of protein occurs only at breakfast and not during other meals.23
GUIDELINE 3: EAT CONSISTENTLY—AND AUTOMATICALLY—FROM DAY TO DAY.
The world is full of contradictions (and not just George Carlin jokes—“why do we drive on a parkway and park on a driveway?”). Our bodies have them, too—like how our stomachs are hungriest at night, but our bodies adapt better when we eat early.
Here’s another: Our brains crave novelty.24 That’s one of the reasons why some of us get excited about new and exotic foods. In general, what’s different makes us excited. What makes us excited floods our brain with feel-good hormones. When we get that flood, we want more—so we keep seeking novelty.
But here’s the catch: Our bodies don’t want that randomized style of eating—this today, that tomorrow—ooh, look, a croissant! Our bodies want consistency. They want to be fed efficiently and with foods that love them to health.
That provides quite a tug-of-war between your reptilian brain and your biology. You will be better off if you can get into a consistent rhythm with your food by following the first two guidelines.
Remember, the purpose of the circadian rhythm is to optimize energy balance. It works by priming the body to be ready at the right time for certain activities to occur. Keeping the size of meals consistent from day to day will help align your eating with your circadian rhythm. An interesting study even showed that people who vary their energy intake from day to day are more likely to have metabolic syndrome (a condition that yields unhealthy numbers in a variety of markers, such as blood pressure and blood sugar), as well as an increased waist circumference.25 Another study examined what happened to blood glucose and lipids in women who ate either their normal diets with regular frequency or meals and snacks with an irregular frequency for 14 days. Irregular eating led to increased insulin resistance and higher levels of LDL (bad) cholesterol.26 A different study by the same group found that people who ate regularly burned more calories after meals and had lower total and LDL cholesterol as well as less insulin resistance.27
What to Do Now: Try to keep all of your meals and snacks the same size every day. One way you can do this is to automate your food choices. Eat the same few options for at least two meals and two snacks a day, so you don’t have to think about what’s healthy. Once you find foods and recipes that you love, have them a lot. Try to incorporate different ingredients into your same recipes once in a while to encourage a diverse microbiome. The more you can automate your actions (the same delicious and healthy meals for breakfast and lunch, with small variations, five days a week), the easier it is to get into the rhythm of smart eating. This will save you from making bad decisions. Plan ahead, keep it simple, choose what you love and what loves you back, and pick some meals that you can keep consistent.
GUIDELINE 4: STOP STEREOTYPING FOOD.
One of the things we hope you take away from this book is that pancakes and omelets aren’t the only things that you can flip. You can also flip stereotypes on their heads. What do we mean? Well, who says you can’t have eggs for dinner or a salad for breakfast? Just because our culture has reinforced certain foods to be eaten at certain times of day doesn’t mean that’s the way it should work. Many international cultures do a very good job of not stereotyping food. Recently a friend of Dr. C’s sent him a picture of his breakfast while in Shanghai; it looked like a typical dinner plate—noodles, rice, fish, lots of vegetables, and larger portions.
In fact, throughout this book you will learn to eat different things at different times of day. Black bean burgers make for sensational day-starting meals, and a bowl of filling oatmeal with some walnuts? That may be your new norm for dinner. When you get past the cultural assumptions we make about food, you will open up your world to a new set of “rules”—and new opportunities for tastes.
If you want to maximize your health by eating in tune with your circadian rhythm, you have to forget societal norms around what foods belong with what time of day. Especially if you follow our guidelines and begin to front-load your day, you’re going to have to rethink what constitutes “breakfast” and “lunch.” Instead of adding extra calories early in the day with the traditional simple carb bombs associated with these meals, we want you to eat your dinner for breakfast or lunch.
Ideally, your breakfast and/or lunch should contain protein, fat, and whole grains. Dinner should be light. The ideal dinner is a salad or other green leafy vegetables. (Make sure to eat small bits of salad—that is, cut it up and chew it well. That way, you’ll get more nitrates and better function from your blood vessels, as well as take advantage of all the benefits of fiber.)
Remember, your body is most insulin resistant at night, so you want to avoid simple carbs at dinner. Instead, have fiber-rich vegetables and proteins. The fiber can help you feel full longer, so you’re not tempted to eat after dark. Plus, if you’ve followed the rules and ate most of your calories early, you should be much less hungry in the evening than you were before following our plan.
Now, the easiest (and healthiest) way to eat your dinner for breakfast or lunch is to actually still make dinner at night just like you always do—but to put most of it away for the next day. For example, Dr. R loves salmon burgers, quinoa, and broccoli for dinner. Instead of eating four burgers (they’re small!) at night, he makes the four in the evening along with quinoa and broccoli but eats only one with a salad for dinner and has the rest of the meal for breakfast.
Dr. C is one of those people who just couldn’t eat a big breakfast even though he knows he should. So he started slow by eating a plain full-fat Greek or Icelandic yogurt (these are strained so they are richer in protein than regular yogurt and have great texture), made from grass-fed milk with some berries. Now, he is cooking quick meals like whole grain pasta or seared salmon with wilted kale and a side of avocado toast (on whole grain bread, of course). If he doesn’t have time in the morning, he sticks with yogurt and has a meal centered on plants and whole grains (what he used to eat for dinner) for lunch.
What to Do Now: Plan out your meals so that your biggest are the first two of the day, and eat a lighter dinner—a salad with a small portion of protein, for example. The following plan encompasses all four of our guidelines to help you take the thinking out of it.
Now, it’s time to put the principles into action. And you don’t have to go from 0 to 60 in one day. We’ll give you plenty of ramp-up time to nudge your eating habits into the When Way style.
What’s the Deal With Intermittent Fasting?
Diet trends come and go—cabbage soup, paleo, keto, you name it. Some are rooted in science, some in marketing. One of the most popular topics in conversation today is rooted in some very interesting science. Intermittent fasting—a catchall to describe various methods of restricted eating—does appear to have benefit for weight loss, health, and longevity.
Most of the data come from studies in simple organisms and animals, where fasting has been shown to increase the life span of bacteria, yeast, worms, and mice. Studies in animals have also suggested that fasting may slow the development of some cancers and the degeneration of brain cells. Fasting can also reduce inflammation and blood pressure, as well as increase insulin sensitivity.28
Of course, fasting is very difficult, so scientists have been studying how to mimic its potential benefits with less extreme diets. That’s when (ta-da!) the concept of intermittent fasting was born.
This kind of eating plan can mean not eating at all every other day, severely restricting energy consumption on two or more nonconsecutive days a week, or even time-restricted feeding (shortening the window in which you eat). The advantage of intermittent fasting over many other diets is that you get to eat as you like on the nonfasting days (within reason, of course; you cannot mainline whole pizzas).
A fascinating study by Valter Longo and colleagues from the Department of Gerontology and Longevity Institute at University of Southern California examined the effects of an intermittent fasting diet on markers of health and disease. The plan they used consisted of five days of energy restriction a month (about a third of normal calorie consumption—1,000 calories the first day and then 750 calories a day for the next four days, with all calories sourced from plant-based foods). During the rest of the month, subjects in the fasting group ate normally. After three months, those in the fasting group lost more weight than those in the control group (who just ate normally), with most of the loss a result of losing fat. And most of the fasters saw a drop in markers of inflammation, as well as a possible increase in stem cell life span.29 That implies a longer life span with less disability. Although more research in humans is needed, the practice is worth further experimentation.
If you’re following the When Way guidelines, you should already be fasting around 12 hours each night—from sunset (dinner) to sunrise (breakfast). If you’re willing to give it a try, the science suggests that you may get some additional benefits from stretching this window out a little further to 14 hours, and then 18. Not eating for most of the day causes your body to burn up all its circulating glucose, as well as stored glycogen; as a result, insulin levels begin to fall. Instead of burning sugar for fuel, your body starts to rely on stored fat, which can be more easily mobilized as a result of low insulin levels.30 In fact, a study in young adult men showed that the mobilization of fat from storage increases rapidly between 18 and 24 hours.31 Scientists theorize that the periodic switching of fuel sources may be a key factor in the advantages that intermittent fasting diets have demonstrated in the lab.32