Good news if you hate the gym, bad news if you’ve invested your time, money, and faith in the body-shaping power of daily workouts: despite what most people think, there still isn’t overwhelming evidence that exercise will reduce weight. Over the past several decades, research continues to show that exercise will definitely increase your body’s energy needs but not always reduce fat, and that a sedentary lifestyle and obesity are linked but not in a proven cause-and-effect relationship. Meanwhile, the popular press has promoted and mythologized a sort of “faith-based” concept of exercise as a key requirement for weight loss.
When the Finnish investigators looked at the results of the dozen best-constructed experimental trials that addressed weight maintenance–that is, successful dieters who were trying to keep off the pounds they had shed–they found that everyone regains weight. And depending on the type of trial, exercise would either decrease the rate of that gain (by 3.2 ounces per month) or increase its rate (by 1.8 ounces).
This is why official guidelines are so weirdly neutral on the subject, saying regular exercise will “promote and maintain health,” for example, or that you should exercise to “avoid unhealthy weight gain.”
The one thing that might be said about exercise with certainty is that it tends to makes us hungry. Maybe not immediately, but eventually. Burn more calories and the odds are very good that we’ll consume more as well. And this simple fact alone might explain both the scientific evidence and a nation’s worth of sorely disappointing anecdotal experience.