Influences of calorie restriction and age on energy expenditure in the rhesus monkey

Abstract

Caloric restriction (CR) is known to retard the aging process, and a marker of aging is decreased energy expenditure (EE). To assess longitudinal effects of CR on EE in rhesus monkeys ( Macaca mulatta), data from 41 males (M) and 26 females (F) subjected to 9 or 15 yr of CR were studied. EE and body composition of monkeys 11–28 yr of age were measured using indirect calorimetry and dual X-ray absorptiometry. Total EE (24-h EE) was divided into daytime (day EE), nighttime (night EE), and daytime minus nighttime (D − N EE). M calorie-restricted monkeys showed a lower 24-h EE (means ± SD = 568 ± 96 kcal/day, P < 0.0001) than controls (C; 630 ± 129 kcal/day). Calorie-restricted M had a lower night EE (difference = 36 kcal P < 0.0001) compared with C M, but after adjusting for FFM and FM, night EE was not different between calorie-restricted and C males ( P = 0.72). The 24-h EE decreased with age (13 kcal decrease/yr, P < 0.0001), but there was no difference between CR and C. Adjusted for FFM and FM, D − N EE decreased with age (9 kcal/yr, P < 0.0001), with no interaction with age ( P = 0.72). The F were compared with age-matched M selected from the male cohort. F had a lower 24-h EE (496 ± 84 kcal/day) than M (636 ± 139 kcal/day) ( P < 0.0001). Adjusting for FFM and FM, night EE was lower in F compared with M (difference = 18 kcal, P = 0.077). Night EE did not differ between calorie-restricted and C younger monkeys after adjusting for FFM and FM. In conclusion, CR did not alter the age-related decrease in EE with CR.