It's time to bust the myth that anyone, and that includes athletes, can outrun a bad diet, say experts in an editorial in the British Journal of Sports Medicine. Excess carbohydrates, not physical inactivity, are behind the surge in obesity.

Regular exercise is key to staving off serious disease, such as diabetes, heart disease, and dementia, write the authors, but our calorie-laden diets now generate more ill health than physical inactivity, alcohol, and smoking - combined. The evidence they cite suggests that up to 40% of those within a normal weight (BMI) range will nonetheless harbor harmful metabolic abnormalities typically associated with obesity.

But few people realize this, and many wrongly believe that obesity is entirely due to lack of exercise, a perception that is firmly rooted in  health advocacy and therefore corporate marketing. Gyms and fitness books are happy to promote the idea and since so many studies say it, so are food companies: It isn't the food, it is being lazy, the authors note. After all, gyms sell sodas and chips on the premises, which puts food under the health halo of exercise.

Public health messaging does not help, because it promotes the idea of a 'healthy weight' through calorie counting, but it's the source of the calories that matters, they point out. "Sugar calories promote fat storage and hunger. Fat calories induce fullness or satiation," they write. 

The prevalence of diabetes increases 11-fold for every 150 additional sugar calories consumed daily, compared with the equivalent amount of calories consumed as fat, they say. The evidence now suggests that carbs are no better, they add. Recent research indicates that cutting down on dietary carbohydrate is the single most effective approach for reducing all of the features of the metabolic syndrome and should be the primary strategy for treating diabetes, with benefits occurring even in the absence of weight loss.