All food has caloric content, so the term "negative calorie foods" may sound misleading. Some scientists say that since some foods are harder for the body to digest, the net effect of eating them creates a calorie deficit. In other words, the body burns more calories processing negative calorie foods than the foods actually contain. In theory, the more of these foods you eat, the less calories you take in, making them great for those trying to lose weight. However, negative calorie food diets are controversial, and not everyone agrees that negative calorie foods even technically exist. In any case, the fruits and vegetables on the negative calorie list are still healthy foods that should be included in any balanced diet. Negative Calorie Berries Berries are unique among the negative calorie foods in that they contain moderate amounts of protein. Protein is extremely important in dieting, and many people forget they need it, preferring instead to sacrifice heavier foods in fav