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IV. Life Stages

         

Basal Energy Expenditure

Basal Energy Expenditure (BEE, also called basal metabolic rate, or BMR):

This is the energy needed to carry out fundamental metabolic functions, such as breathing, ion transport, normal turnover of enzymes and other body components, etc.

It is measured with the subject in the fasted state, lying quietly in a room of comfortable temperature.

BEE may be expressed in terms of surface area: kJ m^-2 hr^-1. This allows a fair comparison among infants, adults, the lean, the obese, etc.

BEE varies between the sexes. Lean body mass is a major determinant, and women tend to have more body fat (less lean muscle mass). As a result, their BEE is lower than that of otherwise comparable males.

The basal energy expenditure varies with age.

• The peak is in infancy.
• It declines rapidly through childhood and adolescence.
• It continues to fall slowly with increasing age.
  • The decline in old age is due largely to loss of muscle.
  • This is not inevitable.
  • The cause is inactivity (absolute or relative).
  • Weight-bearing exercise will prevent or reverse muscle loss among the elderly.

There can be major nutritional consequences to the decline of the REE in advanced age.

• Decreased caloric requirements may lead to decreased food intake.
• Sufficiently low caloric intake can lead to deficient intake of essential nutrients.