What is the energy value of proteins, fats and carbohydrates?

Proteins have an energy value of 17.2 kJ / g, fats have 38.9 kJ / g, and carbohydrates have a nutritional value of 17.2 kJ / g. Proteins and carbohydrates have the same nutritional value in both kJ / g and kcal / g. When food is broken down, carbohydrates are primarily used to provide energy to the body. Protein is needed as a building material. They are broken down into amino acids, and then reassembled into proteins the body needs. Fats have an energetic function, therefore people who are engaged in hard physical labor consume a lot of fatty foods, as they have a high energy value.