Truth About Negative Calorie Foods

68 percent of adult Americans are overweight and therefore many search for an effective weight loss program. A lack of patience and effort occasionally leads to diets and programs promising quick and easy products and services. One of the diets is based on the idea that some foods have negative calories. Consumption of these foods purportedly will promote weight loss because they burn more calories through digestion than they actually have.

Function

Foods contain nutrients that provide energy measured as calories. Food is converted to energy for the purpose of providing fuel for body functions and physical activity. When the amount of calories in the foods consumed is lower than the amount of calories burned, extra energy is obtained from stored fat. This results in an imbalance in calories. When the imbalance reaches 3500 calories, a reduction of one pound of body weight occurs.

Effects

Weight loss programs are based on the concept of increasing the amount of calories burned while consuming foods with decreased amounts of calories. Metabolism, the rate at which your body burns calories, may determine the success or failure of a weight loss program. Calories are burned through body functions such as breathing, muscle contractions, supplying blood and digesting food.

Theories/Speculation

Foods such as asparagus, apples, broccoli, carrots, celery, lettuce, grapefruit and pineapples are believed to be negative calorie foods, because they are considered harder to breakdown and convert into energy and thus require more energy for their digestion. With such a low calorie count, digesting them uses more calories than they actually have. The idea is that eating them will purportedly reduce body fat and body weight. Such foods also provide a surplus of digestive enzymes that increase chemical reactions and metabolism.

Misconceptions

The so-called negative calorie foods are very low in calories. However, the estimation of the amount of calories used for digestion is severely over-estimated. Food has a thermic effect, the energy used by digestion, that is measured as a percentage of the amount of calories. The thermic effect falls between five and 25 percent of total calories consumed. Protein is believed to have a 25 percent digestion rate while fats and carbohydrates use between five to ten percent. For example, a protein serving of 100 calories uses 25 calories to digest. A fat or carbohydrate serving of 100 calories uses between five and ten calories for digestion. Very low calorie foods use significantly fewer calories to burn. In order for negative foods to exist, the thermic effect would have to be over 100 percent.

Expert Insight

Instead of selecting foods because they are believed to have negative calories, foods should be selected based on suggested dietary guidelines. Proper nutrition combined with increased physical activity will help reduce excess body weight.