DR. PETER ATTIA is the cofounder of Nutrition Science Initiative (NuSi), an organization dedicated to improving the quality of science in nutrition and obesity research. A few years ago, he was an elite long-distance swimmer, one of only a dozen or so people to have swum from Los Angeles to Catalina Island. A physician himself, he followed the standard prescribed diet high in carbohydrates and trained religiously for three to four hours daily. He was also, by his own estimation, about forty pounds (18 kilograms) overweight with a body mass index of 29 and 25 percent body fat. But isn’t increasing exercise the key to weight loss?
Caloric imbalance—increased caloric intake combined with decreased caloric expenditure—is considered the recipe for obesity. Up until now, we’ve assumed that exercise was vitally important to weight loss—that by increasing exercise, we can burn off the excess calories that we eat.
THE LIMITS OF EXERCISE: A HARSH REALITY
CERTAINLY, EXERCISE HAS great health benefits. The early Greek physician Hippocrates, considered the father of medicine, said, “If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health.” In the 1950s, along with increasing concern about heart disease, interest in physical activity and exercise began to grow. In 1955, President Eisenhower established the President’s Council on Youth Fitness. By 1966, the U.S. Public Health Service began to advocate that increasing physical activity was one of the best ways to lose weight. Aerobics studios began to sprout like mushrooms after a rainstorm.
The Complete Book of Running by Jim Fixx became a runaway bestseller in 1977. The fact that he died at age fifty-two of a massive heart attack was only a minor setback to the cause. Dr. Kenneth Cooper’s book The New Aerobics was required reading in the 1980s where I went to high school. More and more people began incorporating physical activity into their leisure time.
It seemed reasonable to expect obesity rates to fall as exercise rates increased. After all, governments around the world have poured millions of dollars into promoting exercise for weight loss, and they succeeded in getting their citizens moving. In the United Kingdom from 1997 to 2008, regular exercise increased from 32 percent to 39 percent in men and 21 percent to 29 percent in women.1
There’s a problem, though. All this activity had no effect on obesity at all. Obesity increased relentlessly, even as we sweated to the oldies. Just take a look at Figure 4.1,2.
Figure 4.1. The increasing worldwide prevalence of obesity.
The phenomenon is global. A recent eight-country survey revealed that Americans exercised the most—135 days per year compared to a global average of 112 days. The Dutch came in last at 93 days.3 Weight loss was the main motivation for exercise in all countries. Did all this activity translate into lower rates of obesity?
Glad you asked. The Dutch and Italians, with their low exercise rates, experienced less than one-third the obesity of those iron-pumping Americans.
The problem was apparent in the American NHANES data as well. From 2001 to 2011, there was a general increase in physical activity.4 Certain areas (Kentucky, Virginia, Florida and the Carolinas) increased exercise at Herculean rates. But here’s the dismal truth: whether physical activity increases or decreases, it has virtually no relationship to the prevalence of obesity. Increasing exercise did not reduce obesity. It was irrelevant. Certain states exercised more. Other states exercised less. Obesity increased by the same amount regardless.
Is exercise important in reducing childhood obesity? The short answer is no. A 2013 paper 5 compared the physical activity (measured using accelerometry) of children aged three to five years to their weight. The authors concluded there is no association between activity and obesity.
What went wrong?
Inherent to the Calories In, Calories Out theory is the idea that reduced physical activity plays a key role in the obesity epidemic. This idea is that we used to walk everywhere, but now we drive. With the increase in laborsaving devices such as cars, our exercise has decreased, leading to obesity. The proliferation of video games, television and computers is also believed to contribute to a sedentary lifestyle. Like any good deception, this one sounds pretty reasonable at first. There is a small problem, though. It is just not true.
Researcher Dr. Herman Pontzer studied a hunter-gatherer society living a primitive lifestyle in the modern day. The Hadza in Tanzania often travel 15 to 20 miles per day to gather food. You might assume that their daily energy expenditure is much higher than a typical office worker. Pontzer discusses the surprising results in a New York Times article: “We found that despite all this physical activity, the number of calories that the Hadza burned per day was indistinguishable from that of typical adults in Europe and the United States.”6
Even if we compare relatively recent activity rates to those of the 1980s, before the obesity epidemic came into full swing, rates have not decreased appreciably.7 In a Northern European population, physical-activity energy expenditure was calculated from the 1980s to the mid 2000s. The surprising finding was that if anything, physical activity has actually increased since the 1980s. But this study’s authors went one step further. They calculated the predicted energy expenditure for a wild mammal, which is predominantly determined by body mass and ambient temperature. Compared to its wild- mammal cousins such as the seemingly vigorous cougar, fox and caribou, Homo obesus 2015 is not less physically active.
Exercise has not decreased since hunter-gatherer times, or even since the 1980s, while obesity has galloped ahead full steam. It is highly improbable that decreased exercise played any role in causing obesity in the first place.
If lack of exercise was not the cause of obesity epidemic, exercise is probably not going to reverse it.
CALORIES OUT
THE AMOUNT OF calories used in a day (Calories Out) is more accurately termed total energy expenditure. Total energy expenditure is the sum of basal metabolic rate (defined below), thermogenic effect of food, non-exercise activity thermogenesis, excess post-exercise oxygen consumption and, of course, exercise.
Total energy expenditure = Basal metabolic rate + Thermogenic effect of food + Nonexercise activity thermogenesis + Excess post-exercise oxygen consumption + Exercise.
The key point here is that total energy expenditure is not the same as exercise. The overwhelming majority of total energy expenditure is not exercise but the basal metabolic rate: metabolic housekeeping tasks such as breathing, maintaining body temperature, keeping the heart pumping, maintaining the vital organs, brain function, liver function, kidney function, etc.
Let’s take an example. Basal metabolic rate for a lightly active average male is roughly 2500 calories per day. Walking at a moderate pace (2 miles per hour) for forty-five minutes every day, would burn roughly 104 calories. In other words, that will not even consume 5 percent of the total energy expenditure. The vast majority (95 percent) of calories are used for basal metabolism.
Basal metabolic rate depends on many factors, including
Nonexercise activity thermogenesis is the energy used in activity other than sleeping, eating or exercise; for instance, in walking, gardening, cooking, cleaning and shopping. The thermogenic effect of food is the energy used in digestion and absorption of food energy. Certain foods, such as dietary fat, are easily absorbed and take very little energy to metabolize. Proteins are harder to process and use more energy. Thermogenic effect of food varies according to meal size, meal frequency and macronutrient composition. Excess post-exercise oxygen consumption (also called after- burn) is the energy used in cellular repair, replenishment of fuel stores and other recovery activities after exercise.
Because of the complexity of measuring basal metabolic rate, nonexercise activity thermogenesis, thermogenic effect of food and excess post-exercise oxygen consumption, we make a simple but erroneous assumption that these factors are all constant over time. This assumption leads to the crucially flawed conclusion that exercise is the only variable in total energy expenditure. Thus, increasing Calories Out becomes equated with Exercise More. One major problem is that the basal metabolic rate does not stay stable. Decreased caloric intake can decrease basal metabolic rate by up to 40 percent. We shall see that increased caloric intake can increase it by 50 percent.
EXERCISE AND WEIGHT LOSS
CONVENTIONALLY, DIET AND exercise have been prescribed as treatments for obesity as if they are equally important. But diet and exercise are not fifty- fifty partners like macaroni and cheese. Diet is Batman and exercise is Robin. Diet does 95 percent of the work and deserves all the attention; so, logically, it would be sensible to focus on diet. Exercise is still healthy and important—just not equally important. It has many benefits, but weight loss is not among them. Exercise is like brushing your teeth. It is good for you and should be done every day. Just don’t expect to lose weight.
Consider this baseball analogy. Bunting is an important technique, but accounts for only perhaps 5 percent of the game. The other 95 percent revolves around hitting, pitching and fielding. So it would be ridiculous to spend 50 percent of our time practicing the bunt. Or, what if we were facing a test that is 95 percent math and 5 percent spelling? Would we spend 50 percent of our time studying spelling?
The fact that exercise always produces less