What is Thermic Effect of Food?
Feeding induces a rise of metabolic rate due to the processes of digestion, absorption, and short-term storage of macronutrients. In other words, it takes energy to process and store energy. This is what is called the thermic effect of food, a.k.a. the thermic effect of feeding or dietary induced thermogenesis. The terms "thermic effect of food" and "thermic effect of feeding" are equivalent and both conveniently abbreviate to TEF. The other term, "diet-induced thermogenesis, is abbreviated as DIT.
Contrary to some statements, there appears to be no significant difference in the thermic effect of food bewteen lean and obese people consuming the same amount of calories with the same macronutrient composition. In fact, the effect increases linearly with caloric intake and is independent of leanness and obesity .
On the other hand, the TEF/DIT effect can be broken down by nutrient type as the energy required to process and store different macronutrients varies depending on the type of macronutrient being consumed. Proteins require multiple times more energy to process and store than do both fat and carbs. Fat has the least contribution to thermic effect of food. Due to this, the overall thermic effect of feeding varies depending on the macronutrient mix of the person's diet.
While it is commonly assumed that the thermic effect is about 10% of energy intake, that is a poor approximation in many cases. For example, it is approximately true only for a balanced diet of 50% carbohydrates, 25% proteins, and 25% fats (10.63% of energy intake), but varies between 6% and 13% in some dietary mixes, as illustrated below:
Effect of Macronutrient Balance on Diet-Induced Thermogenesis
The table below presents values for thermic effect of feeding (TEF) as energy value and as percentage of total intake for a few common dietary choices. All tabulated values were calculated using this thermic effect of food calculator.
| Diet | Macro Mix (C/P/F) | TEF (kCal / day) | TEF as % of Intake |
|---|---|---|---|
| High Carb | 60% / 25% / 15% | 278 | 11.13% |
| DASH Diet | 55% / 27% / 18% | 283 | 11.33% |
| Moderate Diet | 50% / 25% / 25% | 265 | 10.63% |
| Zone Diet | 40% / 30% / 30% | 281 | 11.25% |
| Low Carb | 30% / 40% / 30% | 325 | 13.00% |
| Keto Diet | 10% / 15% / 75% | 159 | 6.38% |
In the above table the thermic effect of food is calculated based on an intake of 2,500 kCal per day.