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, T 3 , 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 < 0 kcal: 23.0 hour (20.8‐23.4) vs 21.1 hour (4.7‐22.3), P = .048; WDEB < −300 kcal: 21.8 hour (17.8‐22.4) vs 17.6 hour (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 <0 kcal and <−300 kcal were inversely associated with RMR ratio ( 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.