... This statement applies to amount of energy intake necessary. It is a natural development that our body changes during the course of our life. This is also the case concerning the proportions of body fat and muscle mass. Generally, the body fat increases and the muscles mass diminishes.
The more fat our body has, the less energy we need, as body fat is a inactive body tissue. Complementary, the more muscles we have the higher our energy requirement become, as muscles are an active body tissue with a higher energy consumption than fat. An increase of muscle mass is only possible through strength training or other physical activity.
As a rule of thumb: the older we get, the energy we need since in general the body fat will increase and the muscle mass will decrease.

Basal metabolic rate and total energy expenditure

When we speak of energy the two terms basal metabolic rate (BMR) and total energy expenditure (TEE) come into play. But what exactly do they mean? It is quite simple. The basal metabolic rate is the amount of energy our body needs while resting in order to sustain all fundamental functions, e.g. breathing, the functioning of our kidneys and that our heart keeps beating.
If we move or start to think our energy requirement increases. The energy we need for the basic functions and the additional energy required for activities together make up the total energy expenditure. This total energy expenditure corresponds to the amount of calories we need to eat each day. The daily energy intake requirement varies by age and sex.

Appropriate Nutrients

In order to survive we not only need the adequate amount of energy but also sufficient vitamins and mineral nutrients. A balanced and versatile diet provides us with these micronutrients. But if the amount of foods consumed is reduced the supply may be ensured. Therefore it is of special importance to keep the levels of vitamins and mineral nutrients in mind. Nutrients which are especially critical are vitamin D, calcium and folic acid.