Why We Eat
There are 3 basic needs that are fulfilled by the foods we eat.
Provides Energy
Repairs and Grows Tissues
Regulates Metabolism
Our bodies need a minimum intake of food energy to sustain their metabolism and to drive their muscles. Foods are composed mainly of carbohydrates, fats, proteins, water, vitamins, and minerals. Carbohydrates, fats, proteins, and water represent virtually all the weight of food, with vitamins and minerals making up only a small percentage of the weight.
When you exercise you create "microtrauma" which is a fancy way to say tiny damage to the muscle fibers. When microtrauma occurs (from weight training or other strenuous activities), the body responds by replacing the damaged tissue and adding more of it, so that the risk of repeat damage is reduced. The foods you eat can help repair and grow those muscle fibers.
When it comes to food's effect on metabolism, first we need to explain (in simple terms) what food does to it. Your metabolism increases whenever you eat, digest, and store food. Protein has a higher effect compared with fats and carbohydrates because it takes longer for your body to burn protein and absorb it. But that doesn't mean that fats and carbs don't have an important role to play. Well balanced meals and overall diet are very important.