Energy requirements and aging.

OBJECTIVE To summarise the literature on energy requirements and aging. DESIGN An analysis and review of published data on components of energy expenditure and total energy expenditure (TEE). SETTING Data on basal metabolic rate (BMR) and TEE were obtained from the US Institute of Medicine of the National Academies database (all available data from studies published before 2001, collected from 20 researchers willing to provide individual subject results). SUBJECTS Those individuals from the database who were 20-100 years of age. RESULTS TEE and physical activity level (PAL, defined as the ratio of total to resting energy expenditure) declined progressively throughout adult life in both normal weight and overweight men and women. In normal weight individuals (defined as body mass index (BMI) 18.5-25.0 kg m(-2)) TEE fell by approximately 150 kcal per decade, and PAL fell from an average of 1.75 in the second decade of life to 1.28 in the ninth decade. Thermic effect of feeding data from other published studies indicated no consistent change associated with aging. CONCLUSIONS Aging is associated with progressive declines in resting and TEE, which have implications for defining dietary energy requirements at different stages of adult life.