ESTIMATION OF TOTAL ENERGY NEEDS
The energy requirement of an individual is the level of energy intake from food that will balance energy expenditure when the individual has a body size and composition and level of physical activity, consistent with long term good health, and that will allow for maintenance of economically necessary and socially desirable activity. In children and pregnant and lactating women, the energy requirement includes the energy needs associated with the deposition of tissues or the secretion of milk at rates consistent with good health. (WHO)
Energy requirements are best determined by measurements of energy expenditure.
Energy expenditure from a physiological point of view is made up of three major components:
(i) BMR (ii) Dietary Thermogenesis (iii) Physical activity
For all practical purposes, the component of energy expenditure related to regulatory energy output or dietary thermogenesis are known to merge into measurements related to the cost of physical activity. Hence energy expenditure has only two principal component i) BMR & ii) Physical activity.
Calculation of energy requirements. 1) Predicting BMR.
Equations for predicting BMR (K.cal / 24 hrs) as proposed by the ICMR expert committee for Indians is given in table-20E.
To maintain daily energy balance the total energy requirement of an individual is the number of K cal necessary to replace daily basal metabolic loss in addition to loss from exercise and other physical activities.
Obesity represents an energy imbalance resulting from an excess of energy input over energy output (expenditure). Extreme weight loss is a state of energy imbalance resulting from a deficit energy input over energy output.