Energy requirements and intake

An individual's energy requirements are defined as "the quantity of energy needed to compensate for expenditure and to ensure a body size and composition compatible with the long-term maintenance of good health and physical activity adapted to the economic and social context" (WHO, 1996). By evaluating the various expenditure items, it is possible to roughly estimate individual energy requirements. This assessment must take into account the anthropometric characteristics (weight, height) and physical activity of each individual.

An individual's overall energy expenditure is mainly made up of spending on :

• its basal metabolic rate (energy used at rest to run organs such as the digestive tract, kidneys, brain and heart); this is the main component (60-70%) of energy expenditure

• physical activity (energy used for travel, household, professional and sporting activities); this is the second-largest source of energy expenditure (20-30%)

• dietary thermogenesis (energy used for digestion, intestinal absorption and food storage); this component accounts for only 10% of total energy expenditure

Energy intake

• Theenergy provided by carbohydrates (1 gr. of carbohydrate provides 4 kcal) is rapidly available. It is constantly being used up by the body. The body has very few reserves (in the form of glycogen stored in the liver and muscles). It is therefore important to provide it on a daily basis.

• Theenergy provided by lipids (1 gr. of lipids provides 9 kcal) is not used immediately, but is stored in the body, in adipose tissue reserves, and is used when the body lacks carbohydrate energy (during prolonged effort or in the event of an overall energy deficit).

• Proteins also provide energy by breaking down when used (1 gr. of protein provides 4 kcal).