Age but not menopausal status is linked to lower resting energy expenditure

Abstract

Background: Uncertainty remains whether ageing before late adulthood and menopause reduce fat-free mass and fat mass-adjusted resting energy expenditure (REEadj). We therefore investigated whether REEadj differs 1) between middle-aged and younger women and 2) in middle-age by menopause status. We repeated the age group comparison between middle-aged mothers and their daughters to partially control for genotype. We also explored whether oestradiol and follicle-stimulating hormone concentrations or body fat percentage 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) aged 22–38 and group III (n=59) aged 41-58 years. Group III women were 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: Group I had 126 kcal/d (95% confidence interval [CI], 93–160; P<0.001) higher REEadj than group III, while group II had 88 kcal/d (CI, 49-127; P<0.001) higher REEadj. Furthermore, the daughters had 100 kcal/d (CI, 63-138; P<0.001) higher REEadj than their mothers. In group III, REEadj did not differ by menopause status, but body fat percentage was positively associated with REEadj (beta=0.39, P=0.003). Conclusions: We demonstrated that REE declines with age in women before late adulthood, even when controlling for body composition and partially for genetic background, and that menopause does not contribute to the decline in REEadj. Menopause-associated fat accumulation may actually elevate REEadj.

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

“…All participants had used MHT for at least 4 months, most having used it for years. Details concerning menopausal status determination and MHT preparations used by the women are in the Supplementary Data ( 27 ).…”

“…REE was measured in all studies using the same Vmax Encore 92 metabolic cart (Sensormedics, Yorba Linda, CA, USA) and ventilated hood in the same thermoneutral laboratory; the cart was calibrated accordingly before each measurement. The REE assessment details are in the Supplementary Data ( 27 ). Measurements were performed in the morning after overnight fasting, with resting periods of 0 to 30 minutes and measurement periods of 15 to 30 minutes.…”

“…We excluded at least the first 5 minutes of measurement data; for all participants, we located a steady-state period of at least 5 minutes during which the coefficient of variation was 10% or less for V̇O 2 and V̇CO 2 , and we calculated REE with the modified Weir equation ( 28 ). We made REE comparable between different-sized participants using residuals—the differences between measured and predicted values—from a linear regression model generated using the data of the study sample [Supplementary Table S1 ( 27 )]:…”

“…Herein, we refer to residual REE as REE adj . We also built 3 alternative explanatory models [Supplementary Table S1 ( 27 )]: the first included age as a covariate with FFM and FM; the second added ALMI to account for differences in muscularity ( 29 ); and, in the third, we added the study data collection period as a covariate to examine potential biases introduced by including data from 2 different time periods.…”

“…We performed the statistical analyses using R 4.2.1 ( 31 ). The analytic code is available in the Supplementary Data ( 27 ). We report descriptive statistics as means with standard deviations or as medians with first and third quartiles, but we did not test group differences in order to preserve statistical power.…”