Protein is by far the most thermogenic of the macronutrients (protein, carbohydrate, and fat). Due to the high metabolic costs of processing it, protein provides fewer storable kcal. The thermic effect of a mixed meal is about 10% of intake, while the thermic effect of protein per se is more like 25-30%. That could mean reving up your metabolism by 200 kcal just from your 200-gram (800 kcal) protein intake.