Age But Not Menopausal Status Is Linked to Lower Resting Energy Expenditure

CONTEXT: It remains uncertain whether aging before late adulthood and menopause are associated with fat-free mass and fat mass–adjusted resting energy expenditure (REE(adj)). OBJECTIVES: We investigated whether REE(adj) differs between middle-aged and younger women and between middle-aged women with different menopausal statuses. We repeated the age group comparison between middle-aged mothers and their daughters to partially control for genotype. We also explored whether serum estradiol and FSH concentrations explain REE(adj) in midlife. METHODS: We divided 120 women, including 16 mother-daughter pairs, into age groups; group I (n = 26) consisted of participants aged 17 to 21, group II (n = 35) of those aged 22 to 38, and group III (n = 59) of those aged 41 to 58 years. The women in group III were further categorized as pre- or perimenopausal (n = 19), postmenopausal (n = 30), or postmenopausal hormone therapy users (n = 10). REE was assessed using indirect calorimetry, body composition using dual-energy X-ray absorptiometry, and hormones using immunoassays. RESULTS: The REE(adj) of group I was 126 kcal/day [95% confidence interval (CI): 93-160] higher than that of group III, and the REE(adj) of group II was 88 kcal/day (95% CI: 49-127) higher. Furthermore, daughters had a 100 kcal/day (95% CI: 63-138 kcal/day) higher REE(adj) than their middle-aged mothers (all P < .001). In group III, REE(adj) was not lower in postmenopausal women and did not vary by sex hormone concentrations. CONCLUSIONS: We demonstrated that REE(adj) declines with age in women before late adulthood, also when controlling partially for genetic background, and that menopause may not contribute to this decline.