Sex differences and indications of metabolic compensation in within-day energy balance in elite Division 1 swimmers

Applied Physiology, Nutrition, and Metabolism, Ahead of Print. To determine whether mismatched energy intake and expenditure across the day and associated sex differences may be related with metabolic compensation and/or negative health outcomes, we assessed total-day and hourly energy balance (TDEB and EB), total-day and hourly energy intake (TDEI and EI), total-day and hourly energy expenditure (TDEE and EE) and within-day energy balance (WDEB) in elite male and female swimmers (n  = 25; 18–22 years). Total triiodothyronine (TT3), resting metabolic rate (RMR), and the ratio of actual-to-predicted RMR were determined. Males exhibited higher TDEB (+758 ± 702 kcal vs +52 ± 505 kcal, t-test; p = 0.007) than females. Males exhibited a more positive hourly EB, driven b y greater hourly EI at 11:00, 13:00, 16:00, and 19:00 h (ANOVA, p <  0.05), while EE did not differ. TT3 was negatively correlated with consecutive hours of negative EB (R = −0.604, p = 0.049) and positively correlated to hours in EB (R = 0.740, p = 0.009) in those exhibiting metabolic suppression (n = 12). In individuals in TDEB (n = 21), “backloader s” (consumption of ≥50% daily kcals at or after 1700 h) had lower TT3 (79.3 ng/dL vs 92.9 ng/dL, p = 0.009) than “nonbackloaders” (n = 12). WDEB analyses indicate a greater risk of energy deficiency in females and may capture indices of metabolic compensation not evident with EB anal yses alone.
Source: Applied Physiology, Nutrition, and Metabolism - Category: Physiology Authors: Source Type: research