On my most recent birthday, one of my closest friends texted me a message that included the particularly sweet well-wish, “I hope you have the most beautiful day, and you get a kitten, and you find out cheese has no calories.” That cheese bit would change my life, and probably yours, too, but sadly, it’s not meant to be. Alas, calorie-free dairy is a nutritional unicorn, only slightly more when-pigs-fly than the popular but misguided notion of negative-calorie foods, or foods that burn more calories than they contain.
“It’s a huge myth. There’s no food you can eat that subtracts calories from your body,” Brigitte Zeitlin, M.P.H., R.D., C.D.N., founder of the New York-based BZ Nutrition, tells SELF. It is often thought that foods like celery, lettuce, and broccoli—foods that are super low-cal, replete with water, and/or tough to chew—actually give you a net calorie burn as you eat them. Some people think things like watermelon and chicken breast fall into that category, too. But Abby Langer, R.D. and owner of Abby Langer Nutrition in Toronto, tells SELF they don’t—no food does.
There is a nugget of truth to this idea of negative-calorie foods, but it doesn’t actually work that way in the real world.
“When you consume food, your body does use calories to burn it,” Langer explains. This is what’s called the thermogenic effect of food, or the amount of calories it takes to digest anything you eat. So, yes, your body uses energy (measured in calories) to do the work of digestion. But not a whole lot. That’s because using calories from food is a big part of what keeps your body alive, so it’s streamlined the process into something that doesn’t take much energy to accomplish.
“Broccoli has very few calories, but it wont take your digestive system even more calories to burn those off,” Zeitlin says. Same with celery. So even if you ate nothing else—which we really, really don’t recommend—the negative-calorie theory still falls apart; the amount you’d need to eat would still mean you took in more calories than than the food would burn. Let’s be real, “You’re eating all sorts of other stuff, too—you’re not going to exist on celery,” Langer says.
That’s not to say these foods don’t have their benefits.
“The types of foods that are usually credited as being ‘negative-calorie,’ like celery, apples, broccoli, asparagus, and cabbage, are all low in calories and high in fiber,” Zeitlin says. Fiber is a key player in your health due to its role in preventing metabolic issues like heart disease and cholesterol issues. And if you’re looking to lose weight, fiber is even more useful. “When your diet is full of a lot of ‘negative-calorie’ foods, yes, you can lose weight,” Zeitlin says. But it’s not because your body burns more calories digesting these foods than they contain, it’s because in addition to not having many calories, their fiber fills you up, helping keep you fuller longer and reducing your likelihood of snacking on less nutritious foods.
Instead of trying to eat “negative-calorie” food, many experts urge the exact opposite: moving away from focusing on calories altogether.
Sure, it’s helpful to generally know which foods are high and low in calories, both for health and weight-maintenance or weight-loss purposes. But studies show that many nutritional labels don’t accurately report the calorie content of food, and you don’t absorb all the calories from the things you eat anyway. Plus, counting calories can easily escalate into obsessively tracking your food in an unhealthy way.
Lastly, not all calories are equal, Langer adds, meaning that it’s not correct to think of 100 calories of candy and 100 calories of fruit as the same for your body. All of the above is why many experts prefer for people to focus on quality, not calories.
“Why not concentrate on nourishing your body instead of just eating foods that are lowest in calories? That’s so much healthier, emotionally and physically,” Langer says.
Load your diet with whole foods like a variety of fruits and vegetables, lean sources of protein, and whole grains, Zeitlin says. “That’s what’s going to help you you maintain a healthy weight and make sure your body is working at its most efficient,” she says. No unicorns or flying pigs required.