The female athlete triad (Triad), links low energy availability (EA), with menstrual dysfunction (MD), and impaired bone health. The aims of this study were to examine associations between EA/MD and energy metabolism and the prevalence of Triad-associated conditions in endurance athletes. Forty women [26.2 ± 5.5 years, body mass index (BMI) 20.6 ± 2.0 kg/m(2) , body fat 20.0 ± 3.0%], exercising 11.4 ± 4.5 h/week, were recruited from national teams and competitive clubs. Protocol included gynecological examination; assessment of bone health; indirect respiratory calorimetry; diet and exercise measured 7 days to assess EA; eating disorder (ED) examination; blood analysis. Subjects with low/reduced EA (< 45 kcal/kg FFM/day), had lower resting metabolic rate (RMR) compared with those with optimal EA [28.4 ± 2.0 kcal/kg fat-free mass (FFM)/day vs 30.5 ± 2.2 kcal/kg FFM/day, P < 0.01], as did subjects with MD compared with eumenorrheic subjects (28.6 ± 2.4 kcal/kg FFM/day vs 30.2 ± 1.8 kcal/kg FFM/day, P < 0.05). 63% had low/reduced EA, 25% ED, 60% MD, 45% impaired bone health, and 23% had all three Triad conditions. 53% had low RMR, 25% hypercholesterolemia, and 38% hypoglycemia. Conclusively, athletes with low/reduced EA and/or MD had lowered RMR. Triad-associated conditions were common in this group of athletes, despite a normal BMI range. The high prevalence of ED, MD, and impaired bone health emphasizes the importance of prevention, early detection, and treatment of energy deficiency.