SDA(Specific Dynamic Action) shows that the consumption of foods is associated with an expenditure of energy. It's a form of wasted energy, which amounts to 6-10% of total food intake as heat. The proportion of macronutrients contributing to SDA is : protein~30%, carbohydrate~6%, lipid~4%. (But mix food of high protein content with carbohydrate and fat can reduce SDA of protein to ~10%.) Thus calorie valus of protein determined from bomb calorimeter is ~5.7kcal/g with only ~70% of it (thus ~4kcal/g) does work.
