A food can be considered a negative calorie food if it's calorie level is so low that eating and digesting it uses up more energy than the food itself provides. If you ate nothing but such foods, you would eventually starve to death.
What is Negative Calorie food?
The term "negative calorie food" is something of a misnomer. Scientifically speaking, there is no such thing as a negative calorie - A calorie is a unit of heat and as such cannot be negative.
This being the case, why do people call certain food "negative calorie food"?
A food can be considered a negative calorie food if it's calorie level is so low that eating and digesting it uses up more energy than the food itself provides. If you ate nothing but such foods, you would eventually starve to death. An oft sited example is water. Drinking a glass of water provides no calories at all, yet the body must expend some calories simply to bring the water up to your body's temperature, so the simple act of drinking a glass of cold water uses up a few calories.
In practice, such foods are rare. Below is a list of "negative calorie food" but few of them, by themselves provide fewer calories than they take to digest, but it must be remembered that the body is constantly expending energy all the time just in order to breathe and remain alive. A food such as Celery for example, does not provide enough calories to digest itself AND keep the body going whilst doing so - The net result is a loss of calories and hence it qualifies as a "negative calorie food"
As mentioned above, a diet that consisted exclusively of negative calorie food would result (pretty quickly) in nutritional deficiencies, and eventually death from starvation.
A healthier way to use a negative calorie food diet is to use it in place of fasting, or as a form of detox. This is something you can do for between 1 - 3 days, perhaps after a period of overindulgence (i.e the Christmas period). As with all dietary regimes it is always a good idea to check it out with your own doctor beforehand.
If you do decide to detox using negative calorie food, it is wise to keep the following points in mind
1. Always use a wide variety of foods. Confining yourself to one type of food (especially fruit), to the exclusion of all others can be damaging to the body so be sure to consume a range of available foods.
2. Do not eat all day. There should be enough bulk in the foods to stave off hunger, especially if used for only a couple of days at a time. It is much better to plan four or five negative calorie meals a day and allow you digestive system to rest between them.
3. Always chew the food thoroughly. This will not only make the food more satisfying and easier to digest, but will also use up more calories, enhancing the negative calorie food effect.
4. Be aware that as with fasting or any kind of detox regimen, it is possible that you may encounter some uncomfortable symptoms such as headaches, tiredness, depression and irritability. If such symptoms become prolonged or severe - Stop the diet and consult your doctor.
List of Negative Calorie Food: