Papageorgiou M, et al. – This study compared the impacts of low energy availability (EA) on bone turnover markers (BTMs) between women and men. As per within group comparisons, decreased bone formation and increased bone resorption was evident in women, but not in men, as a result of low EA (15 kcal·kg LBM (lean body mass)^-1·d^-1) for five days. In addition, no sex specific differences were detected.

Methods

• Researchers performed these studies using a randomised, counterbalanced, crossover design.
• This study included eleven eumenorrheic women and eleven men who were asked to complete two 5-day protocols of controlled (CON; 45 kcal·kg LBM^-1·d^-1) and restricted (RES; 15 kcal·kg LBM^-1·d^-1) EAs.
• Participants ran daily on a treadmill at 70% of their peak aerobic capacity (VO₂ peak) resulting in an exercise energy expenditure of 15 kcal·kg LBM^-1·d^-1 and consumed diets providing 60 and 30 kcal·kg LBM^-1·d^-1.
• Researchers analyzed blood for BTMs [β-carboxyl-terminal cross-linked telopeptide of type I collagen (β-CTX) and amino-terminal propeptide of type 1 procollagen (P1NP)], markers of calcium metabolism [parathyroid hormone (PTH), albumin-adjusted calcium (ACa), magnesium (Mg) and phosphate (PO₄)] and regulatory hormones [sclerostin, insulin-like growth factor 1 (IGF-1), triiodothyronine (T₃), insulin, leptin, glucagon-like-peptide-2 (GLP-2)].

Results

• Findings showed that, in women, β-CTX AUC was significantly higher (P = 0.03) and P1NP AUC was significantly lower (P = 0.01) in RES compared to CON.
• Researchers oberved that, in men, neither β-CTX (P = 0.46) nor P1NP (P = 0.12) AUCs were significantly different between CON and RES.
• They noted no significant differences between sexes for any BTM AUCs (all P values > 0.05).
• Data reported that insulin and leptin AUCs were significantly lower following RES in women only (for both P = 0.01).
• In addition, results revealed that there were no differences in any AUCs of regulatory hormones or markers of calcium metabolism between men and women following RES (all P values > 0.05).