The problem, as he and his contemporaries saw it, is that light exercise burns an insignificant number of calories, amounts that are undone by comparatively effortless changes in diet. In 1942, Louis Newburgh of the University of Michigan calculated that a 250-pound man expends only three calories climbing a flight of stairsthe equivalent of depriving himself of a quarter-teaspoon of sugar or a hundredth of an ounce of butter. He will have to climb twenty flights of stairs to rid himself of the energy contained in one slice of bread! Newburgh observed. So why not skip the stairs, skip the bread, and call it a day?
More-strenuous exercise, these physicians further argued, doesnt help mattersbecause it works up an appetite. Vigorous muscle exercise usually results in immediate demand for a large meal, noted Hugo Rony of Northwestern University in his 1940 textbook, Obesity and Leanness. Consistently high or low energy expenditures result in consistently high or low levels of appetite. Thus men doing heavy physical work spontaneously eat more than men engaged in sedentary occupations. Statistics show that the average daily caloric intake of lumberjacks is more than 5,000 calories, while that of tailors is only about 2,500 calories. Persons who change their occupation from light to heavy work or vice versa soon develop corresponding changes in their appetite. If a tailor becomes a lumberjack and, by doing so, takes to eating like one, why assume that the same wont happen, albeit on a lesser scale, to an overweight tailor who decides to work out like a lumberjack for an hour a day?
Clinicians, researchers, exercise physiologists, even personal trainers at the local gym took to thinking and talking about hunger as though it were a phenomenon exclusive to the brain, a question of willpower (whatever that is), not the natural consequence of a body trying to replenish itself with energy. Ultimately, the relationship between physical activity and fatness comes down to the question of cause and effect. Is Lance Armstrong excessively lean because he burns off a few thousand calories a day cycling, or is he driven to expend that energy because his body is constitutionally set against storing calories as fat? If his fat tissue is resistant to accumulating calories, his body has little choice but to burn them as quickly as possible: what Rony and his contemporaries called the activity impulsea physiological drive, not a conscious one. His body is telling him to get on his bike and ride, not his mind. Those of us who run to fat would have the opposite problem. Our fat tissue wants to store calories, leaving our muscles with a relative dearth of energy to burn. Its not willpower we lack, but fuel.
). The only thing about doing things like me is that if you want to keep your weight down, you have to be committed to changing your diet permenently. You can't go back to eating a bunch of junk and expect to stay slim, even if you are exercizing. I mean, you can treat yourself here and there, but not going overboard...