Thermic Effect of Food
topic
The thermic effect of food (TEF) is the energy expenditure of digesting, absorbing, and metabolizing ingested nutrients — accounting for approximately 10% of total daily energy expenditure on average, with significant variation by macronutrient: protein (20–30% of its own calories lost to digestion), carbohydrates (5–10%), and fats (0–3%). Higher-protein diets therefore produce greater thermogenic metabolic contribution, meaning that equal caloric intakes with different protein proportions result in different net energy availability.
Role
The thermic effect of food is one of the most practically relevant but least popularly understood aspects of caloric metabolism — explaining why high-protein diets produce greater fat loss than calorie-matched lower-protein diets even without changes in exercise or hunger: the metabolic cost of processing protein is built into every high-protein meal. The person who understands TEF appreciates that 100 calories of chicken breast and 100 calories of olive oil produce different net caloric contributions and different hormonal responses — a nuance that the simple calorie-counting framework completely obscures.