Anegative-calorie food is food that supposedly requires morefood energy to bedigested than the food provides. Its thermic effect orspecific dynamic action—the caloric "cost" of digesting the food—would be greater than its food energy content. Despite its recurring popularity indieting guides, there is no evidence supporting the idea that any food is calorically negative. While some chilled beverages are calorically negative, the effect is minimal[1] and requires drinking very large amounts of water, which can be dangerous, as it can causewater intoxication.
There is no evidence to show that any of these foods have a negative calorific impact.[2][3] Foods claimed to be negative in calories are mostly low-calorie fruits and vegetables such ascelery,grapefruit,orange,lemon,lime,apple,lettuce,broccoli, andcabbage.[4] However, celery has athermic effect of around 8%, much less than the 100% or more required for a food to have "negative calories", unless you freeze the celery, but then it would be too hard to chew and you would have to blend it to consume it in smoothie form while it's still at freezing temperature.[5]
Diets based on negative-calorie food do not work as advertised but can lead to weight loss because they satisfy hunger by filling the stomach with food that is not calorically dense.[4] A 2005 study based on a low-fatplant-based diet found that the average participant lost 13 pounds (5.9 kg) over fourteen weeks, and attributed the weight loss to the reduced energy density of the foods resulting from their low fat content and high fiber content, and the increased thermic effect.[6] Nevertheless, these diets are not "negative-calorie" since they bear energy. Another study demonstrated that negative-calorie diets (NCDs) have the same efficacy to low-calorie diets (LCDs) in inducing weight loss when both of these diets are combined with exercise.[7]
Chewing gum has been speculated as a "negative-calorie food"; A study on chewing gum reportedmastication burns roughly 11 kcal (46 kJ) per hour.[8] Therefore, to reach "negative-calorie" one has to chew for almost 6 minutes per kcal (one chewing gum can have a large range of kcal from around 2 to 15 kcal).
What are these magic foods? Just the low-calorie, high-nutrient-density fruits and vegetables that you might expect to be recommended to someone who is dieting: celery, grapefruit, lemon, lime, apple, lettuce, broccoli, cabbage, and other such items.
