The process of eating provides your body with energy, but it also requires energy to accomplish. The thermic effect of food (TEF), also called diet-induced thermogenesis, is the energy your body uses to digest, absorb, and process the nutrients from the food you consume. This metabolic cost of digestion means that a portion of the calories from the food you eat is burned simply through the act of processing it.
For most healthy adults eating a standard, balanced diet, TEF accounts for about 10% of their daily calorie intake. For instance, if you consume 2,000 calories in a day, approximately 200 of those calories will be expended just to process that food.
The Science of the Thermic Effect
The energy expenditure associated with the thermic effect of food is directly tied to the chemical makeup of the food itself, specifically its macronutrient content. Your body must work harder to break down some macronutrients compared to others, resulting in a higher energy cost. This variation creates a clear hierarchy in the thermic effect of proteins, carbohydrates, and fats.
Protein stands out as the macronutrient with the most significant thermic effect. When you consume protein, your body uses approximately 20-30% of its calories for digestion and metabolism. This is due to the complex processes involved in breaking down proteins into amino acids and preparing them for use in the body.
Carbohydrates have a moderate thermic effect, with an estimated 5-10% of their calories being used during the digestive process. The specific TEF for carbohydrates can vary depending on their complexity; high-fiber, complex carbohydrates tend to have a higher thermic response because they are digested more slowly. Fats are the easiest for the body to process, requiring the least amount of energy. The thermic effect of fat is estimated to be between 0-3% of its caloric content.
This difference in energy expenditure means that the macronutrient composition of a meal is a primary determinant of its overall thermic effect. Two meals with the same total calorie count can have different impacts on your metabolism based on their protein, carbohydrate, and fat ratios. A meal higher in protein will result in a greater increase in metabolic rate post-consumption compared to a meal that is higher in fat.
Examples of High-Thermic Foods
Because protein has the highest thermic effect, foods rich in this macronutrient are considered high-thermic. Incorporating these foods can increase the energy your body expends during digestion.
Lean protein sources are excellent examples of high-thermic foods. Chicken breast, turkey, and lean cuts of pork and red meat require a significant amount of energy to digest due to their high protein content. Similarly, wild-caught seafood, especially fatty fish like salmon, offers a dual benefit. It provides high-quality protein that boosts thermogenesis while also delivering beneficial omega-3 fatty acids. Eggs are another accessible and versatile option, with each egg containing a substantial amount of protein.
Legumes and lentils are plant-based powerhouses that offer both protein and fiber, making them particularly effective high-thermic foods. A single cup of black beans, for example, contains a significant amount of both nutrients. Other varieties like chickpeas, pinto beans, and lentils also contribute to a higher metabolic cost of digestion. Fiber-rich grains such as quinoa, oats, and brown rice also have a notable thermic effect compared to more refined grains.
Certain foods contain specific compounds that can temporarily increase metabolic rate. Chili peppers, for instance, contain capsaicin, a compound that has been shown to increase thermogenesis. Green tea contains antioxidants known as catechins, which can also contribute to a higher energy expenditure.
The Role in Metabolism and Weight Management
The thermic effect of food is one of three major components of your body’s total daily energy expenditure (TDEE). The other two are your basal metabolic rate (BMR), which is the energy used for basic functions at rest, and the energy expended during physical activity. TEF typically accounts for about 10% of your TDEE, making it a smaller contributor than BMR and physical activity.
While choosing high-thermic foods can increase the number of calories you burn, it is important to view this as one part of a larger picture. The impact of TEF on overall energy balance is modest. Shifting the macronutrient composition of your diet towards protein can increase this number, but it remains a relatively small fraction of total expenditure.
The concept of “negative-calorie” foods, which supposedly burn more calories to digest than they contain, is a popular myth. There is no scientific evidence to support the idea that any food has a net negative caloric impact. Foods often cited in this category, like celery, are very low in calories, but the energy required to digest them is still less than the energy they provide. Diets based on these foods may lead to weight loss only because they are low in caloric density, not because they actively burn more calories than they contain.