Despite forcing himself to do a rigorous amount of aerobic exercise, John Cloud hasn't budged from 163 pounds—with gut fat. Shouldn’t all that exercise change something? Not necessarily, he writes for Time. Science has shown that exercise has much less effect than diet on overall weight. The problem, he writes, is that exercise prompts you to eat more.
The scenario for zero-sum weight change goes like this: A human being sits in front of a computer all day, then goes to the gym for 45 minutes of intense exercise. But that bout of activity increases hunger and weakens self-control, increasing the likelihood of snacking on some fries afterward—fries they probably wouldn’t have craved without the exercise. The eating induced by exercise often cancels out, weight-wise, what exercise achieved. The lesson? Weight-watchers should try to be more consistently active throughout their day, and pay attention to diet.