The standard oxygen consumption value equivalent to one metabolic equivalent (3.5 ml/min/kg) is not appropriate for elderly people.

In epidemiological studies, estimation of total energy expenditure can only be carried out from using metabolic equivalent (MET) units calculated physical activity questionnaires, where 1 MET is generally assumed to be 3.5 ml/min/kg resting oxygen consumption (VO2 resting). Since the basal metabolic rate varies with age, the energy expenditure equivalent to 1 MET is likely to vary with age. The objective of this study was to determine the energy value for 1 MET in elderly Chinese people compared with younger subjects, using a cross-sectional study. The participants were 138 young adults (88 female, 50 male) aged 16-64 years and 70 elderly adults (35 female, 35 male) aged 65-89 years. VO2 resting was determined by indirect calorimetry (Deltatrac; Datex Division Instrumentraium Corp, Helsinki, Finland). The height and weight were measured. The body fat percentage and lean mass was estimated by body mass index, tricep and bicep skinfold thickness and Bio-impedance analysis. Both VO2 resting and VO2 resting/kg body weight were significantly lower in elderly than young subjects in both gender groups (P<0.01). The significant age difference in VO2 resting remained after adjustment for weight, height and lean mass in both the male group (P<0.001) and the female group (P<0.01). In conclusion, age had an independent effect on VO2 resting, independent of the change of body composition. The present study suggested that the assumption of 1 MET=3.5 ml/min/kg VO2 resting may over-estimate energy expenditure when apply to elderly people.