Some of the calories in the food you ingest will be used to digest, absorb, and metabolize the rest of the food, and some will be burned off as heat. This process is known under various names, notably diet-induced thermogenesis (DIT), specific dynamic action (SDA), and thermic effect of food (TEF).
TEF represents about 10% of the caloric intake of healthy adults eating a standard mixed diet, but your actual number will depend on several factors, which include your lean body mass and the size and composition of your meal. The energy required to digest each macronutrient (its TEF) can be expressed as a percentage of the energy provided by this macronutrient:
Fat provides 9 food calories per gram, and its TEF is 0–3%.
Carbohydrate provides 4 food calories per gram, and its TEF is 5–10%.
Protein provides 4 food calories per gram, and its TEF is 20–30%.