Background/Objectives: This study investigates age-dependent changes in different components of energy expenditure (EE) within the longitudinal study on nutrition and health status in an aging population in Giessen, Germany (GISELA). Subjects/Methods: Between 1994 and 2006, data obtained at a total of 3033 visits from 363 women and 153 men with a mean initial age of 67.4 ± 5.9 and 66.9 ± 5.2 years, respectively, were evaluated. The mean duration of follow-up was 8 years.Resting metabolic rate (RMR) was assessed by indirect calorimetry and physical activity patterns were assessed by questionnaire. EE of physical activity and total EE (TEE) were calculated using multipliers for RMR. Energy intake was determined through a validated 3-day estimated dietary record. Linear mixed models were used to analyze the influence of age on EE adjusted for covariates. Results: Resting metabolic rate decreased in women and men by 158 and 326 kJ/d per decade, respectively; after considering changes in body composition and fat distribution, respective decreases were 81 and 286 kJ/d per decade. EE of physical activity decreased similarly in both sexes (472 kJ/d per decade). TEE dropped in women and men by 540 and 823 kJ/d per decade, respectively. No statistically significant changes in energy intake and body weight were observed in the course of follow-up. Conclusions: The age-dependent decrease in TEE is mainly due to a decrease in physical activity. The stable energy intake and body weight of the GISELA subjects may be indicators for a relatively good health status.

These results indicate that the decline in RMR with advancing age cannot be totally due to changes in body composition.

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