Lower Energy Availability Is Associated With Low Resting Enrgy Expenditure In Japanese Female Athletes.

Abstract

Adequate energy availability (EA) is important for the health of female athletes. EA is calculated by subtracting exercise energy expenditure from total energy intake, and normalizing by fat-free mass (FFM). The international consensus statement indicates that reproductive function, energy metabolism, endocrine function, and bone health are affected by the threshold of EA, which falls below 30 kcal/kg FFM/day. However, several previous studies have reported that low EA is not associated with menstrual function or metabolism. Further, these data have been based on active women of Caucasian, European, or European-American descent. There are no published scientific studies regarding EA in Asian athletes. PURPOSE: To investigate the relationship between EA and resting energy expenditure (REE) in Japanese female athletes. METHODS: Fifteen collegiate athletes participated in this study. Menstrual status was based on self-reported menstrual history and confirmed by the ovulation test kit. Energy intake was determined by 3-day weighed food records. Exercising energy expenditure was assessed by the HR-VO2 method. REE was measured by indirect calorimetry using the Douglas bag technique during the early follicular phase. Body composition was measured by dual-energy X-ray absorptiometry (DXA). RESULTS: Subjects with lower EA (<25 kcal/kg FFM/day) had lower REE/FFM than those with normal EA (23.2±3.1 vs. 27.0±2.4 kcal/kg FFM/day, p<0.05), and had lower triiodothyronine (T3) levels (80±8 vs. 101±9 ng/dl, p<0.01). In addition, energy intake level was significantly lower (1615±317 kcal/day vs. 2102±364 kcal/day, p<0.05) in subjects with lower EA. However, the levels of estradiol, insulin-like growth factor 1, luteal hormone, follicle stimulating hormone, and progesterone were not significantly different between the two groups. CONCLUSIONS: In Japanese female athletes, energy metabolism was suppressed in subjects with lower EA, which was under 25 kcal/kg FFM/day, and was associated with lower REE due to lower T3 levels. Thus, lower EA may influence energy metabolism in Japanese female athletes.