Understanding how many calories your body uses on a daily basis can help you lose or maintain weight. Your resting metabolic rate is the total amount of calories your body burns by maintaining its normal processes and functions. The thermic effect of food adds to that. The thermic effect of food differs according to certain variables.
Thermic Effect of Food
The thermic effect of food refers to the amount of calories your body expends consuming food. This energy accounts for chewing action, digestion and absorption. During digestion, your body must breakdown the nutrients into molecules small enough to absorb and use, which takes energy. During this process, food is moved through the digestive system through wave-like movements of the smooth muscles of the digestive organs, which also uses energy. Finally, transport of the nutrients from the intestine and into the bloodstream takes energy as well, specifically when a means of facilitated transport out of the intestine and into the bloodstream occurs.
Amount and Factors
About 10 percent of the total calories your body burns per day comes from the thermic effect of food, according to the website RD411.com. Certain factors affect how many calories your body expends on digestion and absorption on a daily basis. The amount of calories your meal is made up of, the nutrients that make the calories, your overall diet and your age all play a role. As age increases, the thermic effect of food decreases. Overall, between four and eight hours after food is consumed, an increase in metabolic rate is seen due to the thermic effect of food.
Macronutrients
The three main macronutrients include protein, carbohydrates and fat. These are the nutrients that make up the majority of food you eat. Each macronutrient takes a different amount of energy to breakdown, absorb, and use. Protein is the most complex macronutrient and, therefore, takes the most energy. Fat takes the least amount of energy to metabolize and carbohydrates fall between fat and protein.
Negative Calorie Foods
Some foods are known as "negative calorie" or "calorie burning" foods. This means they have gotten a reputation for costing more energy to breakdown, absorb and use then they are worth. According to Donald Hensrud, M.D. of Mayo Clinic, while this is theoretically possible, it isn't a magic cure for weight loss. The foods that have gotten this reputation are mostly fruits and vegetables, which should be part of a healthy and well-balance diet anyway. But Hensurd warns against limiting yourself to only "negative calorie" foods, as any diet that relies around one food in particular will not provide all the nutrients your body needs.
References
- RD411.com: Energy Expenditure; October 2008
- "Anatomy and Physiology"; Kenneth S. Saladin; 2004
- Calories Per Hour.com: The Thermic Effect of Food
- Mayo Clinic: Negative Calorie Foods: Diet Gimmick or Weight Loss Aid?; Donald Hensrud, M.D.; January 2010
