HUMAN ENERGY-EXPENDITURE IN AFFLUENT SOCIETIES - AN ANALYSIS OF 574 DOUBLY-LABELED WATER MEASUREMENTS

Objectives: To describe average levels of free-living energy expenditu re in people from affluent societies and to determine the influence of body weight, height, age and sex. Design: Analysis of 574 measurement s of total energy expenditure (TEE, assessed by the doubly-labelled wa ter method); basal metabolic rate (BMR, directly measured or derived f rom similar directly measured proxy measures such as during sleep); ac tivity energy expenditure (AEE, derived as TEE - BMR); and physical ac tivity level (PAL, derived as TEE/BMR) from people aged 2-95 years. Th e dataset was extracted from 1614 published and unpublished measuremen ts in 1156 subjects after exclusion of repeat estimates and subjects i n special physiological or behavioural states (eg pregnancy, athletic or military training etc). Results: A separate analysis of data from n on-ambulant subjects, and from elite endurance athletes (ail excluded from the main dataset) established the limits of human daily energy ex penditure at around 1.2 x BMR and 4.5 x BMR. In the main analysis, the validity of PAL as an index of TEE adjusted for BMR was tested and co nfirmed. Regression equations were then derived to describe TEE, BMR, AEE and PAL in terms of body weight, height, age and sex. As anticipat ed, TEE, BMR and AEE were all positively related to weight and height, while age was a negative predictor, especially of activity. The influ ence of weight disappeared when TEE was expressed as PAL, but height a nd age remained as highly significant predictors. For all three compon ents, females expended 11% less energy on average than males after adj ustment for weight, height and age. Average levels of energy expenditu re in different age and sex groups are tabulated. Conclusions: There n ow exists a large and robust database of energy expenditure measuremen ts obtained by the doubly-labelled water method. Analysis of the data from affluent societies shows that, in general, levels of energy expen diture are similar to the recommendations for energy requirements adop ted by FAO/WHO/UNU (1985) and UK Department of Health (1991). PAL valu es for active subjects tend to be higher than is currently assumed. Th e current analysis provides a substantial body of normal data against which other estimates can be compared. Sponsorship: Supported by the M edical Research Council. Descriptors: basal metabolic rate, doubly-lab elled water method, energy expenditure, physical activity level