The myth of exercise and weight loss

Gary Taubes's article in New York Magazine gives a nice rundown of the evidence that exercise does not cause weight loss: link. Many of you will already be familiar with this stuff, but I still found Taubes's article an interesting and fun read. Three excerpts:

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 impulse”—a 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. It’s not willpower we lack, but fuel.

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[P]ost-workout, we get hungry: Our fat tissue is devoting itself to restoring calories as fat, depriving other tissues and organs of the fuel they need and triggering a compensatory impulse to eat. The feeling of hunger is the brain’s way of trying to satisfy the demands of the body. Just as sweating makes us thirsty, burning off calories makes us hungry.This research has never been controversial. It’s simply been considered irrelevant by authorities, all too often lean, who have been dead set on blaming fatness on some combination of gluttony, sloth, and perhaps a little genetic predisposition thrown in on the side.

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As it turns out, it’s carbohydrates—particularly easily digestible carbohydrates and sugars—that primarily stimulate insulin secretion. “Carbohydrates is driving insulin is driving fat,” as George Cahill Jr., a retired Harvard professor of medicine and expert on insulin, recently phrased it for me. So maybe if we eat fewer carbohydrates—in particular the easily digestible simple carbohydrates and sugars—we might lose considerable fat or at least not gain any more, whether we exercise or not. This would explain the slew of recent clinical trials demonstrating that dieters who restrict carbohydrates but not calories invariably lose more weight than dieters who restrict calories but not necessarily carbohydrates. Put simply, it’s quite possible that the foods—potatoes, pasta, rice, bread, pastries, sweets, soda, and beer—that our parents always thought were fattening (back when the medical specialists treating obesity believed that exercise made us hungry) really are fattening. And so if we avoid these foods specifically, we may find our weights more in line with our desires.

As for those people who insist that exercise has been the key to their weight-loss programs, the one thing we’d have to wonder is whether they changed their diets as well. Rare is the person who decides the time has come to lose weight and doesn’t also decide perhaps it’s time to eat fewer sweets, drink less beer, switch to diet soda, and maybe curtail the kind of carb-rich snacks—the potato chips and the candy bars—that might be singularly responsible for driving up their insulin and so their fat.

Previously and relatedly on Brlogsbane: Compulsory reading about food and nutrition.