Negative calorie foods are a hot discussion topic in the world of dieting. These are substances that supposedly require more energy to digest than they supply to the body. This would mean that eating only negative calorie foods would lead to malnutrition and eventually death through starvation. However, as many of you will already be aware, negative calorie foods are an urban myth. All foods – even very low-calorie ones such as celery and carrots, provide a lot more energy than is needed to digest them. So it turns out the question ‘how many calories do you burn by eating a carrot’ does not make much sense. In fact, the metabolic energy required to digest a carrot is below 10% of its nutritional content.
The only substance that can truly be called a negative calorie intake is water. Water does not contain any calories, but the body uses energy to process it. Therefore, the net result is a negative calorie process. However, by most definitions, water is excluded from the negative calorie substance category as well, because it does not contain any substances vital for diet, such as protein or carbohydrates.