The truth behind negative calorie foods

Imagine a food that actually burns more calories than it provides, that helps you lose weight just by eating it. The idea sounds pretty good, doesn’t it? These so-called negative calorie foods have been promoted by many fitness books and diet plans. But do they work? Is there science to back this claim or is it just another fitness myth?

The Theory

Chewing and digesting food, as with all bodily functions, burns calories without us ever noticing. Certain foods, like celery or grapefruit, are high in dietary fiber but extremely low in calories, leading to the conclusion that they burn more calories than they actually provide.  

The Reality

According to the Mayo Clinic, about five to 10 percent of your daily caloric expenditure goes toward chewing, breaking down and storing your food. The low-calorie options that populate the negative calorie food lists found all over the Internet do, in fact require energy to digest. So, in theory at least, negative calorie foods exist. In practice, however, there is no scientific evidence to support the idea that a single food requires more calories to break down than it provides. The real problem with this diet philosophy comes in the application. When people read that grapefruit is a negative calorie food that will burn calories for you, they react in one of two ways: Either they eat nothing but these negative calories foods, or they add it to their regular diets to try to counteract the calories from other foods.

Nothing In, Nothing Out

The first approach, loading your diet with almost exclusively negative calorie foods will absolutely make you lose weight. But this loss will be rapid and unhealthy. Diets that consist mainly of these foods are severely deficient in both total calories and vital nutrients. These low-calorie, starvation diets can not be sustained for long periods of time and can even backfire. When your body enters starvation mood, your metabolism will slow down and actually start fighting to keep you alive by storing fat for energy. You may also start to lose muscle mass, since that will be broken down for fuel as well.

Too Much of a Good Thing

The other application of negative calorie foods, tacking them onto otherwise unhealthy meals, isn’t much better. A 2010 study from Northwestern University’s Kellogg School of Management tested people’s perception of calories of meals both with and without a healthy side. In one of the tests, subjects were asked to guess the calorie content of a bowl of chili. They estimated the value at about 699 calories. When the chili was served with a side of green beans, though, they placed the meal at 656 calories. In truth, the side of green beans probably didn’t add many more calories, but it certain didn’t detract any either. The belief in negative calorie foods and the practice that it leads to could actually cause you to gain weight by ingesting more calories than you realize. The bottom line: negative calorie foods as a diet philosophy is about as empty as it sounds. You won’t do yourself any good by trying to follow it, and you’re likely to do yourself some harm. Do you have any experience with negative calorie foods? Please share your thoughts with us in the comments.