Negative Calorie Foods - Wishful Thinking
Susan Bowerman, MS, RD, CSSD
Here’s something that sounds too good to be true - negative calorie foods. The concept has been floating around for years, and thinking goes like this: certain foods, like cabbage, lettuce or celery, actually contain fewer calories than the calories your body uses in order to digest and process them. Foods that contain a lot of water and a lot of fiber, and those that require a lot of chewing, have all been touted as negative calorie foods. When you look at individual foods, it almost makes sense, but when you do the math, negative calorie foods don’t add up to a magic bullet for weight loss.
Here’s why. Of all the calories your body expends every day, about 10% of them are spent on processing, digesting and absorbing your food. It’s been suggested, then, that if you eat a 6 calorie stalk of celery, it only takes about a half a calorie to process it - so you end up in negative territory, to the tune of about 5 calories.
But here’s where the idea falls apart. For one thing, that 10% is just an average. Some foods take fewer calories to digest and absorb than others. Fats, for example, require very little energy to process. When people say that fat goes straight to their hips, that’s not far from the truth. Proteins, on the other hand, take more energy to digest and absorb, and carbohydrates lie somewhere in the middle.
And, more importantly, remember this: we eat mixtures of foods in our meals, not just a plate full of so-called negative calorie foods. Which means that, using the same logic, it would take 60 calories to process a 600 calorie meal of chicken, vegetables and mashed potatoes, leaving you squarely in positive calorie territory?
And, even if the negative calorie concept were true, and there have been no scientific studies to actually suggest that it is, you couldn’t subsist solely on these very low calorie foods because you’d be lacking a lot of vital nutrients.
However, there is a reason that these watery, high fiber veggies and fruits are associated with weight loss. They have relatively few calories per bite, so they can fill you up without filling you out. Negative calories or not, including plenty of fresh fruits and veggies as part of a healthy eating plan for weight loss is never a bad idea.