The "Negative Calories" Myth Explained
Simply put, the term “negative calories” refers to food that takes more calories to process than it delivers. Take celery, the usual example of a “negative calorie” food. It wastes its calories first with mastication, then intestinal churning, only to have the fibers slip out the back door.
Positive Negative Calories
But in actuality, there are really no “negative calorie” foods that offer the body zero minus whatever calories. Calories wasted in extracting nutrients are already considered in calculating the Thermic Effect of Food (TEF). TEF usually wastes about 10% of calories, but for some foods, the TEF can reach 20%. Still, that means a 10-calorie stalk of celery wastes 2 calories to deliver 8. Big deal. Since calorie counting is inexact at best, we’ll call those 8 calories a wash.
The concept of “Free Food” has been used forever by dietitians, diabetic educators and Weight Watchers to describe foods with a negligible calorie count that, presumably, one can eat with abandon. Free foods include “negative calorie” foods, like celery, cucumbers, lettuce, spinach, chicory, greens, sprouts, mushrooms, onions, and other vegetables that are basically water and dissolved nutrients wrapped in a bundle of fiber. The only real calories they provide are those that we add. (“Negative calorie” aficionados place fruits like watermelon, mango and apples, on the "free food" list; however, I maintain that fruit has too much easily digested natural sugar to be "free".)
Negative Negative Calories
And so, “negative calories” was a cute term, innocent enough. The concept had no research backing and there was no definitive food list, but what was the harm? But then “negative calories” went out into the world where it became the darling of a group of sensationalized Negative Calorie Diets. Those diets utilized the “Negative Calorie Effect” - the calorie wasting process - usually embellished to claim those foods actually increased calorie burning metabolically. (That just isn’t true.) The negative calorie diets were usually severely restricted in protein and other nutrients from the major food groups. They produce weight loss because they are generally lacking in food.
But the last straw was when big business used the "negative calorie" word one time too many. In 2007, Coca-Cola and Nestle got slapped with a $650,000 fine for saying their green tea drink, Enviga, burned 20 - 33 calories more than it delivered in a 12-ounce can. Business said it was due to “negative calories” but the FDA said the evidence doesn’t support that claim. (I noticed Enviga contains caffeine and EGCG, both of which may boost metabolism. Those "negative calories” look like stimulants to me.)
And so, think fondly of “negative calories” if you will, but don’t make them into something they are not. Tasty, nutritious, filling, very low calorie foods. Log them because they are full of nutrients and they make your analysis look good.
Are you concerned or confused about "negative calorie" foods and diets?