Within-day energy deficiency and reproductive function in female endurance athletes.

Abstract

We aimed to estimate and compare within-day energy balance (WDEB) in athletes with eumenorrhea and menstrual dysfunction (MD) with similar 24-hour energy availability/energy balance (EA/EB). Furthermore, to investigate whether within-day energy deficiency is associated with resting metabolic rate (RMR), body composition, S-cortisol, estradiol, T3 , and fasting blood glucose. We reanalyzed 7-day dietary intake and energy expenditure data in 25 elite endurance athletes with eumenorrhea (n=10) and MD (n=15) from a group of 45 subjects where those with disordered eating behaviors (n=11), MD not related to low EA (n=5), and low dietary record validity (n=4) had been excluded. Besides gynecological examination and disordered eating evaluation, the protocol included RMR measurement; assessment of body composition by dual-energy X-ray absorptiometry, blood plasma analysis, and calculation of WDEB in 1-hour intervals. Subjects with MD spent more hours in a catabolic state compared to eumenorrheic athletes; WDEB<0kcal: 23.0hour (20.8-23.4) vs 21.1hour (4.7-22.3), P=.048; WDEB<-300kcal: 21.8hour (17.8-22.4) vs 17.6hour (3.9-20.9), P=.043, although similar 24-hour EA: 35.6 (11.6) vs 41.3 (12.7) kcal/kg FFM/d, (P=.269), and EB: -659 (551) vs -313 (596) kcal/d, (P=.160). Hours with WDEB <0kcal and <-300kcal were inversely associated with RMRratio (r=-.487, P=.013, r=-.472, P=.018), and estradiol (r=-.433, P=.034, r=-.516, P=.009), and positively associated with cortisol (r=.442, P=.027, r=.463, P=.019). In conclusion, although similar 24-hour EA/EB, the reanalysis revealed that MD athletes spent more time in a catabolic state compared to eumenorrheic athletes. Within-day energy deficiency was associated with clinical markers of metabolic disturbances.