Fat contains twice as many calories per unit weight as carbohydrates does, so fat is an efficient way for animals, who must move about, to store energy. Compare the way fat and carbohydrates interact with water, and explain why this interaction also gives fat an advantage for weight-efficient energy storage.
Carbohydrates are sugars and these are water soluble and can be passed from the body in the urine very easily whereas fatty acids and triglyceride fats are hydrophobic and therefore do not dissolve readily in water.
Carbohydrates giv e the body a short lived buzz from this quick blast of energy.
They are not readily metabolised by the body like simplecarbohydrates and therefore are stored by the body and serve as reserves to be drawn upon when the body requires them.