Low RMR_ratio as a surrogate marker for energy deficiency, the choice of predictive equation vital for correctly identifying male and female ballet dancers at risk

Ballet dancers are reported to have an increased risk for energy deficiency with or without disordered eating (DE) behavior. A low ratio between measured (_m) and predicted (_p) resting metabolic rate (RMR_ratio<0.90) is a recognized surrogate marker for energy deficiency. We aimed to evaluate the prevalence of suppressed RMR using different methods to calculatepRMR and to explore associations with additional markers of energy deficiency. Female (n=20) and male (n=20) professional ballet dancers, 19-35 years of age were enrolled. _mRMR was assessed by respiratory calorimetry (ventilated open hood). _pRMR was determined using the Cunningham and Harris-Benedict equation, and different tissue compartments derived from whole body Dual-energy X-ray Absorptiometry assessment. The protocol further included assessment of body composition and bone mineral density (BMD), blood pressure, DE (Eating Disorder Intervention-3), and for females the Low Energy Availability in Females Questionnaire (LEAF-Q). The prevalence of suppressed RMR was generally high but also clearly dependent on the method used to calculate _pRMR, ranging from 25 to 80% in males and 35 to 100% in females. Five percent had low BMD, while 10% had DE, and 25% hypotension. Forty percent of females had elevated LEAF-Q score, and 50% were underweight. Suppressed RMR was associated with elevated LEAF-Q score in females and with higher training volume in males. In conclusion, professional ballet dancers are at risk for energy deficiency. The number of identified dancers at risk varies greatly depending on the method used to predict RMR, when using RMR_ratio as a marker for energy deficiency.