Free Why We Get Fat: And What to Do About It by Gary Taubes

that allowed them to continue to promote exercise and physical activity, regardless of what the evidence actually showed. One common method was (and still is) to discuss only the results that seem to support the belief that physical activity and energy expenditure can determine how fat we are, while simply ignoring the evidence that refutes the notion, even if the latter is in much more plentiful supply.
    Two experts in the
Handbook of Obesity
, for instance, reported as a reason to exercise that the Danish attempt to turn sedentary subjects into marathon runners had resulted in a loss of five pounds of body fat in male subjects; they neglected to mention, however, that it had zero influence on the women in the trial, which could be taken as a strong incentive not to exercise. (If your goal is to lose weight—even if your health and your life depend on it, as they very well may—would you train to run a twenty-six-mile foot race upon being told that you
might
lose five pounds of fat after a year and half of work?)
    Other experts took to arguing that we could lose weight by weightlifting or resistance training rather than the kind of aerobic activity, like running, that was aimed purely at increasing our expenditure of calories. The idea here was that we could build muscle and lose fat, and so we’d be fitter even if our weight remained constant, because of the trade-off. Then the extra muscle would contribute to maintaining the fat loss, because it would burn off more calories—muscle being more metabolically active than fat.
    To make this argument, though, these experts invariably ignored the actual numbers, because they, too, are unimpressive. If we replace five pounds of fat with five pounds of muscle, which is a significant achievement for most adults, we will increase our energy expenditure by two dozen calories a day. Once again, we’re talking about the caloric equivalent of a quarter-slice of bread, with no guarantee that we won’t be two-dozen-calories-a-day hungrier because of this. And once again we’re back to thenotion that it might be easier just to skip both the bread and the weightlifting.
    Before I finish this discussion of exercise and energy expenditure, I want to return briefly to the guidelines published in August 2007 by the American Heart Association and the American College of Sports Medicine. “It is reasonable to assume that persons with relatively high daily energy expenditures would be less likely to gain weight over time, compared with those who have low energy expenditures,” the expert authors had written. “So far, data to support this hypothesis are not particularly compelling.”
    Damaging as this may be to the notion that we can lose weight by exercising, the authors were unwilling to be definitive. They had slipped in a qualification, the words “so far.” By doing so, they were leaving the door of possibility open. Maybe somebody, someday, would show scientifically that what these experts believed in their hearts to be true really was.
    But they missed the point with their qualification. Here it is: this idea that we get fat because we’re sedentary and we can get lean or prevent ourselves from fattening further by upping our energy expenditure is at least a century old. One of the most influential European authorities on obesity and diabetes, Carl von Noorden, suggested this in 1907. We can, in fact, trace it to the 1860s, when the obese British undertaker William Banting discussed his numerous failed attempts to lose weight in his best-selling
Letter on Corpulence
. A physician friend, wrote Banting, suggested he slim down by “increased bodily exertion.” So Banting took up rowing “for a couple of hours in the early morning.” He gained muscular vigor, he wrote, “but with it a prodigious appetite, which I was compelled to indulge, and consequently increased in weight, until my kind old friend advised me to forsake the exercise.”
    The experts from the AHA and the