ENERGY-COST OF PHYSICAL-ACTIVITY IN 12-WEEK-OLD INFANTS

The energy cost of physical activity has long remained the component o f energy expenditure most difficult to quantify. Measurement of total energy expenditure (TEE) in free-living infants by the doubly-labelled water method permits a new approach. The energy cost of activity was estimated in 12 week infants as the difference between TEE and the sum of minimal metabolic rate, the energy cost of tissue synthesis, and t hermogenesis. No differences were found between the sexes or between b reast-fed and formula-fed infants. However, the cost of activity was s ubstantially higher than previously assumed. The approach is more suit able for use with groups rather than individuals. (C) 1995 Wiley-Liss, Inc.