Why You Can't Out-Exercise a Bad Diet

Doctors say what you eat is more important than how much you move. Credit: Cultura RM / JPM / Getty

According to a recent editorial in the British Journal of Sports Medicine, a false common faith in exercise is blinding much of the public from reforming poor diets. Turns out, when it comes to maintaining a tight waistline, what you eat is more important than how hard you work it off. Over the past 30 years, obesity levels have skyrocketed, even as overall physical activity in the U.S. remained the same. Most scientists now believe that it’s the type of calories consumed that matters. In short, we should be eating more calories from fat, fewer carbs, and way less sugar. "Sugar calories promote fat storage and hunger," write the three authors from the UK’s Academy of Medical Royal Colleges. "Fat calories induce fullness."

The authors suggest media campaigns from the food industry — for instance commercials that associate Sprite and Snickers with sports and exercise — are as destructive to public health as the sugarcoated claims disseminated by the tobacco industry a generation ago. They also cite a recent report in the Lancet that found poor diets now cause more disease than physical inactivity, alcohol and smoking combined. "Members of the public are drowned by an unhelpful message about maintaining a healthy weight through calorie counting,and many still wrongly believe that obesity is entirely due to lack of exercise," the authors write. "You cannot outrun a bad diet."