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 follicle-stimulating hormone 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 17–21, group II (n = 35) of those aged 22–38 and group III (n = 59) of those aged 41–58 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/d (95% CI: 93–160) higher than that of group III, and the REE_adj of group II was 88 kcal/d (95% CI: 49–127) higher. Furthermore, daughters had a 100 kcal/d (95% CI: 63–138 kcal/d) higher REE_adj than their middle-aged mothers (all P < 0.001). 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.