The Relationship Between Body Composition And Lifestyle Behaviors On Hormone Levels In Premenopausal Women

Body composition is linked to hormonal changes that affect metabolic and reproductive health, and these changes may be influenced by sedentary behavior (SB) and exercise (EX). However, research examining these fluctuations between women using hormonal contraceptives (HC) and naturally menstruating (NM) women is limited. PURPOSE: To determine the influence of body composition on sex hormone binding globulin (SHBG), estradiol (E2), progesterone (P4), leptin and adiponectin and the potential associations with SB and EX. METHODS: Premenopausal women (N = 16, HC = 9, NM = 7) completed weekly testing for 8 weeks which included a serum blood draw and self-reported SB and EX. All participants completed a dual energy x-ray absorptiometry scan to assess lean mass (LM), body fat percentage (BF%), visceral adipose tissue (VAT) and bone mineral density (BMD) at baseline. Multilevel models were used to determine whether hormones differ across 8 weeks and their associations with LM, BF%, VAT, SB, and EX. A secondary multilevel model was used to determine whether SB and EX differed across 8 weeks and their associations with LM, BF%, and VAT. A random effect of participant and fixed effect of visit and cycle phase were used as fixed factors in both models. RESULTS: SB was positively associated with BF% (b = 1.9, p = 0.045) and negatively associated with LM (b = -3.0, p = 0.003). No significant associations between EX and BF% and LM existed. E2 was positively associated with EX (b = 23.9, p = 0.006) but not SB. E2 and P4 were positively associated with BMD (b = 25.1, p = 0.013; b = 2.5, p = 0.021, respectively). Leptin was positively associated with BF% (b = 15.3, p < 0.001) and LM (b = 3.5, p = 0.044). Leptin levels were significantly higher during the luteal phase compared to follicular (b = 4.5, p = 0.037). SHBG and adiponectin were not significantly different by cycle phase and showed no significant associations with any other measures included in the analysis. CONCLUSIONS: In an apparently healthy female population, BF% was positively associated with SB and leptin. Leptin levels varied across menstrual cycle phases among NM participants. Among premenopausal women, E2 is more related to EX than body composition measures. These findings are limited by a small sample size; however, the use of advanced modeling enhances the study design.