Introduction

The energy needs of humans are currently estimated from measures of energy expenditure of the individual. Until recently however, in the absence of sufficient data on habitual total energy expenditure of free-living humans, other approaches have enabled us to compute the energy requirements. While estimating the energy requirement of diverse demographic groups within the population, additional provision needs to be made for physiological processes characteristic of these groups. These include the additional provision of energy for optimal growth in infants and children and for the additional energy needs of pregnancy and lactation in women of reproductive age.

Energy requirement has been defined as ‘the amount of food energy needed to balance energy expenditure in order to maintain body size, body composition and a level of necessary and desirable physical activity consistent with long-term good health’ (Food and Agriculture Organization/World Health Organization/United Nations University – FAO/WHO/UNU, 2004). Energy balance is achieved when dietary intake is equal to the energy expenditure plus the energy cost of growth in infancy, childhood and pregnancy, or the energy cost to produce adequate milk during lactation. The recommended dietary intake of energy for a population group which should satisfy these requirements for the attainment and maintenance of optimal long-term good health, physiological functions and well-being is the mean energy requirement of the healthy and well-nourished individuals within this population group.