The thermic effect of food (TEF) is energy expended digesting and processing what you eat. Research shows protein has the highest thermic effect at 20-30% of calories consumed—eat 100 calories of protein, 20-30 are used just processing it. Carbohydrates are 5-10%. Fat is 0-3%. This is one reason protein-rich diets support weight management: more goes to processing, less to storage.
This companion covers understanding thermic effect, the macronutrient hierarchy, and practical implications. (4 min read)