Hello,

Release of energy after complete combustion of food is known as Gross Calorific Value.

• Carbohydrates have a gross calorific value of  4.1 kcal/g
• Proteins  have a gross calorific value of 5.65 kcal/g
• Fats have a gross calorific value of  9.45 kcal/g

You can calculate gross calorific value in Laboratory using BOMB's Calorimeter.

The actual amount of energy liberated in the body from carbohydrates, proteins and fats is called Physiologic Value.

• Carbohydrates have a Physiological value of  4 kcal/g
• Proteins  have a Physiological value of 4  kcal/g
• Fats have a Physiological value of  9 kcal/g

Physiological Value is exact value.

Significant difference can be seen between Physiological and Gross Value as Gross Value is measured using Lab equipments, there is a variation in reading or values.

Hope this was helpful.