We’re blaming the obesity epidemic on the wrong variables.

People have spent decades trying to lose weight by counting calories, eating fat-free foods and exercising. So why is obesity still such a serious problem in the United States? To understand, first we have to look at some of the many misunderstandings surrounding obesity.

Contrary to popular belief, weight gain isn’t caused by a lack of physical activity. In fact, exercise can even be counterproductive when you’re trying to lose weight. We tend to overestimate the number of calories we burn while playing sports, for instance, and it actually takes a lot of effort to burn the calories contained in a single chocolate bar. The bottom line is that you can’t lose weight by spending more time at the gym – and strenuous exercise might make you hungrier or even encourage you to overeat.

“Fat genes” don’t explain our society’s weight problems, either (although they can have some impact on an individual’s body weight). The obesity epidemic is a fairly recent phenomenon, starting in the United States in the 1970s, and then spreading to Europe and Japan. Any genetic changes we might’ve experienced can’t have been expressed that rapidly. Something else has to be going on.

But obesity is also not simply the result of consuming more calories than we burn. People who believe that think we can fix the problem just by eating less. But that doesn’t work. Why? Because, first of all, it’s not that easy just to eat less! Secondly, it’s unhealthy to prioritize certain foods based on their calorie content. A 200-calorie serving of french fries is much more unhealthy, for example, than a 200-calorie serving of nuts.

But most importantly, and perhaps the most harmful misconception about weight loss, is that you can’t lose weight by eating less. You don’t gain weight when your cells have too many calories. You gain weight when your organs aren’t getting enough nutrients from your blood.

If your organs are low on nutrients, a calorie-restricted diet only makes the problem worse. It slows your metabolism and increases your appetite – so a simple weight-loss plan won’t get you very far.