How much energy is produced by each type of macromolecule

The amount of energy you'll get from carbohydrate, protein and fat is measured in calories per gram. Fats have the most energy and proteins have the same amount as carbohydrates, but their value as a source of energy is determined by more than the calories gained from one gram. Other factors, such as your activity level and diet, impact which macronutrient is used for energy.

Carbohydrates- 4kcal per gram
Protein - 4 kcal per gram
Fat - 9 kcal per gram

Where are the "following reasons", I don't think anybody can answer without those, so please try editing you question.