Thermic effect of foodTEF · Diet-induced thermogenesis

The thermic effect of food is the energy your body spends digesting, absorbing, transporting and storing what you eat. It typically accounts for around 10% of total daily energy expenditure, making it the smallest of the major components but not a negligible one.

It varies substantially by macronutrient, and this is the part with practical consequences. Protein costs roughly 20 to 30% of its own energy to process, carbohydrate around 5 to 10%, and fat around 0 to 3%. Alcohol sits somewhere in the middle and is not otherwise useful.

That difference is one of several reasons higher protein diets help with fat loss. Some of the energy in protein is spent handling it, and the effect compounds with protein's greater satiety and its role in preserving muscle during a deficit.

It also means calorie counts are slightly optimistic for high protein foods and slightly pessimistic for fat, though the difference is smaller than the marketing around metabolism boosting foods implies.

Negative calorie foods are a myth built on this idea. Celery does not cost more to digest than it provides; the arithmetic simply does not work at the energy densities involved.

Whole and minimally processed foods do appear to have a somewhat higher thermic effect than heavily processed equivalents of the same macronutrient composition, which is one small contributor to the difference seen in controlled feeding studies.

In practice, this is one of the mechanisms behind protein first, rather than a lever to manipulate. Our macro calculator sets the protein target that captures most of the available benefit.