RESTING METABOLIC-RATE AND DIET-INDUCED THERMOGENESIS IN YOUNG AND ELDERLY SUBJECTS - RELATIONSHIP WITH BODY-COMPOSITION, FAT DISTRIBUTION,AND PHYSICAL-ACTIVITY LEVEL

To investigate the relationship between age and energy expenditure, re sting metabolic rate (RMR) and diet-induced thermogenesis (DIT; for 18 0 min after a 1.3-MJ meal) were measured by indirect calorimetry in 56 young and 103 elderly subjects. In addition, the influence of body co mposition, body-fat distribution, and physical activity level on this relationship was studied. RMR was significantly lower in elderly (3.98 +/- 0.46 and 3.33 +/- 0.39 kJ/min for men and women, respectively) th an in young (5.29 +/- 0.53 and 4.08 +/- 0.33 kJ/min for men and women, respectively) subjects, which persisted after adjustment for body com position. DIT was significantly lower in older than in younger men (12 6 +/- 27 vs 154 +/- 34 kJ/180 min) but not in women (111 +/- 26 vs 115 +/- 25 kJ/180 min). The difference in men disappeared after adjustmen t for body composition. No clear relation between physical activity le vel and RMR or DIT was observed. These results demonstrate a relations hip of age per se with RMR but not with DIT.