Context It remains uncertain whether aging before late adulthood and menopause are associated with fat-free mass and fat mass–adjusted resting energy expenditure (REEadj).

Objectives We investigated whether REEadj 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 REEadj 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 REEadj of group I was 126 kcal/d (95% CI: 93–160) higher than that of group III, and the REEadj 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 REEadj than their middle-aged mothers (all P<0.001). In group III, REEadj was not lower in postmenopausal women and did not vary by sex hormone concentrations.

Conclusions We demonstrated that REEadj declines with age in women before late adulthood, also when controlling partially for genetic background, and that menopause may not contribute to this decline.