Energy Intake and Output Are Balanced Under Steady- State Conditions
Intake of carbohydrates, fats, and proteins provides energy that can be used to perform various body functions or stored for later use. Stability of body weight and composition over long periods requires that a person’s energy intake and energy expenditure be balanced. When a person is overfed and energy intake persistently exceeds expenditure, most of the excess energy is stored as fat, and body weight increases; conversely, loss of body mass and starvation occur when energy intake is insufficient to meet the body’s metabolic needs.
Because different foods contain different proportions of proteins, carbohy-drates, fats, minerals, and vitamins, appropriate balances must also be main-tained among these constituents so that all segments of the body’s metabolic systems can be supplied with the requisite materials.