The thermic effect of food shows how much calories your body uses for digesting and processing the different macronutrients. The thermic effect of the different macronutrients is different. There is no exact numbers, researches show slightly different numbers, but the ballpark numbers are:
Protein is around 20-35%
Carbs 5-15%
Fats 0-5%
What does this mean? If you eat 200 kcal of protein, 40 – 70 kcal your body will use just to process and digest protein. So effectively you’ll only get about 65 – 80% of the protein you eat. For carbs it’s between 75 – 95% and for fats it’s 95 – 100% that the body will get.
It is very important if your goal is to build more muscle and you’re a hardgainer (ectomorph). Your body burns off an excessive amount of calories as heat because of your metabolism being inefficient. You need to make up for it in your nutrition. Since protein has up to 5x higher thermic effect than carbs or fats you should add more carbs or fats into your diet.
Body composition is another important factor here because the leaner you are, you show greater thermic effect.
The thermic effect of food is also higher post exercise. So if you’re a hardgainer, you should consider adding more calories (predominantly from carbs and fats) into your nutrition outside of the post workout window.