Do some foods have negative calories?

THE CLAIM

Some foods have negative calories.

THE FACTS

For years, diets and weight-loss books have boasted that you can eat a piece of food and burn calories at the same time. The idea is that some foods have so few calories that the act of chewing them requires expending more energy than is absorbed, resulting in a calorie deficit and ultimately weight loss.

Topping the list of "negative calorie" foods are vegetables such as cabbage, lettuce, cucumbers and celery. Celery, for example, contains eight to 10 calories a stalk and is 95 percent water.
Chewing most foods typically only burns about five calories an hour, but the act of digesting may require slightly more. That is particularly the case with celery because it is mostly cellulose, a type of fiber that humans do not have the enzymes necessary to properly break down and use.
Cathy Nonas, director of obesity and diabetes programs at North General Hospital in New York City, said that while no hard studies exist, it is possible that snacking on celery might cause a very slight calorie deficit. But the difference would be so minuscule that at the end of the day it would have no real impact unless the celery was replacing other fattening or high-calorie foods.

The other problem is that celery is not only low in calories but also low in vitamins and minerals.
"If you substitute celery for cookies and pretzels, and those are the things that were putting you over the top in terms of weight then, yes, you will lose weight," she said. "But you're not going to lose weight by chewing celery a couple times a day if you're not exercising and changing what else you eat."

THE BOTTOM LINE

It may be possible to expend a few more calories than you absorb eating something like celery, but in the end the deficit is negligible.