Active Women before/after an Intervention Designed to Restore Menstrual Function: Resting Metabolic Rate and Comparison of Four Methods to Quantify Energy Expenditure and Energy Availability

Abstract

It is hypothesized that exercise-related menstrual dysfunction (ExMD) results from low energy availability (EA), defined as energy intake (EI)—exercise energy expenditure (EEE). When EI is too low, resting metabolic rate (RMR) may be reduced to conserve energy.Purpose:To measure changes in RMR and EA, using four methods to quantify EEE, before/after a 6-month diet intervention aimed at restoring menses in women with ExMD; eumenorrheic (Eumen) active controls (n = 9) were also measured.Methods:Active women with ExMD (n = 8) consumed +360 kcal/d (supplement) for 6 months; RMR was measured 2 times at 0 months/6 months. EI and total energy expenditure (TEE) were estimated using 7-day diet/activity records, with EA assessed using four methods to quantify EEE.Results:At baseline, groups did not differ for age, gynecological age, body weight, lean/fat mass, VO2max, EI and EA, but mean TEE was higher in ExMD (58.3 ± 4.4kcal/kgFFM/d; Eumen = 50.6 ± 2.4; p < .001) and energy balance (EB) more negative (–10.3 ± 6.9 kcal/kgFFM/d; Eumen=-3.0 ± 9.7; p = .049). RMR was higher in ExMD (31.3 ± 1.8 kcal/kgFFM/d) vs. Eumen (29.1 ± 1.9; p < .02). The intervention increased weight (1.6 ± 2.0kg; p = .029), but there were no significant changes in EA (0-month range = 28.2–36.7 kcal/kgFFM/d; 6-month range = 30.0–45.4; p > .05), EB (6 months = –0.7 ± 15.1 kcal/kgFFM/d) or RMR (0 months = 1515 ± 142; 6 months = 1522 ± 134 kcal/d). Assessment of EA varied dramatically (~30%) by method used.Conclusions:For the ExMD group, EI and weight increased with +360 kcal/d for 6 months, but there were no significant changes in EB, EA or RMR. No threshold EA value was associated with ExMD. Future research should include TEE, EB and clearly quantifying EEE (e.g.,>4 MET) if EA is measured.