The energy released by complete combustion of one gram of food is gross calorific value.

Gross calorific value of carbohydrates - 4.1 kcal/g
Gross calorific value of proteins - 5.65 kcal/g
Gross calorific value of fats - 9.45 kcal/g

The actual amount of energy liberated in the body from carbohydrates, proteins and fats is called physiologic value of food.

Physiologic value of carbohydrates - 4 kcal/g
Physiologic value of proteins - 4 kcal/g
Physiologic value of fats - 9 kcal/g