Thermic effect of foodTEF · Diet-induced thermogenesis

The thermic effect of food is the energy cost of handling a meal. It accounts for roughly ten per cent of total daily intake for a mixed diet, and it differs sharply by macronutrient: protein costs around 20 to 30 per cent of its own calories to process, carbohydrate roughly 5 to 10 per cent, and fat only about 0 to 3 per cent.

It matters because it is one of the four components of total daily energy expenditure, alongside resting metabolic rate, exercise and NEAT. It is also part of why higher-protein diets have a small metabolic edge beyond their satiety advantage — although the effect is real, it is modest, not a licence to ignore total intake.

In practice you cannot meaningfully manipulate it beyond eating adequate protein and largely unprocessed food. Claims about specific 'fat-burning' or 'negative-calorie' foods overstate a small effect considerably.