Naturally Thermogenic Foods

Thermogenic foods raise your temperature. All food is thermogenic. Whenever you burn calories, you generate heat, and every time you eat, some portion of the calories you consume is spent chewing, swallowing, absorbing, metabolizing and eliminating the food. The amount of energy you use in these processes is referred to as the thermic effect of food. In common use, thermogenic foods are foods that require relatively more calories to consume, digest, metabolize and eliminate. Foods are also commonly considered thermogenic if they increase your metabolism.

Thermic Effect

On average, the thermic effect of food is estimated to be about 10 percent your caloric intake. If you consume 2,000 calories, you'll expend an average of about 200 calories processing that food. Different foods require varying amounts of energy to process. Easily digested, absorbed and metabolized, fats have a thermic effect of 3 percent. You'll burn only 3 calories processing 100 calories of fat. Fruit and fibrous vegetables have a thermic effect of around 20 percent and proteins require the most effort, burning 30 percent of their caloric value.

Urban Myth: Negative Calorie Foods

Some websites wrongly suggest that foods such as celery, berries, broccoli, cabbage, apples, pears and leafy greens such as spinach and lettuce, cause you to burn more calories than the food contains. For the most part, such claims are misinformed. Most of these so-called negative-calorie foods are high-fiber, low-calorie fruits and vegetables. They don't have a lot of calories but only a portion of their caloric-value --- typically around one fifth -- is spent on digesting them. The fiber in these foods slow digestion, stabilize blood sugar and sate your appetite. Also, some of them give you a little extra assistance in your weight loss efforts. Apples and pears contain pectin, a soluble fiber that binds with fat in other food you've eaten while it's in your stomach, so some of the fat you consume is eliminated with your waste rather than absorbed. So by all means, include these foods in your diet, but don't expect miracles.

Low-Fat Protein

Protein foods tend to be high in calories, but close to a third of the calories they contain is expended breaking down the protein. To get the greatest thermogenic effect of protein foods, choose low-fat protein, such as skinless chicken or turkey breast, non-fat milk or dairy products and legumes.

Hot Peppers

Capsaicin, a compound found in cayenne, habaneros and most chile peppers raises your body temperature. Perhaps you've noticed this sometime after you've downed a bowl of five-alarm chili or spicy Buffalo wings. The thermogenic effect of capsaicin is not going to make you sweat off a lot of weight, however. It raises your metabolism by 8 percent for just a couple of hours, according to the November 28, 2006 edition of "The New York Times."

Green Tea

Green tea might be one of the few, true negative-calorie foods. It contains no calories and it has a thermogenic effect. Green tea contains several types of catechins, including epigallocatechin gallate, that appear to increase your metabolic rate. A study published in the February 2008 "Physiology & Behavior" found that over the 12-week study period, subjects who drank green tea lost 7 lbs. more than participants who had an identical diet but didn't drink green tea. Bioassays made several times throughout the study suggested that green tea increased metabolism and enhanced oxidation of fat.