Predictive equations fail to accurately assess resting metabolic rate in international elite male volleyball players

The accurate estimation of daily energy requirements is important to inform athletes about their caloric needs and to prevent long-term low energy availability. Such estimations are often done by estimating energy expenditure. Recent data, including from a 200+ athlete cohort, show systematic underprediction of resting metabolic rate (RMR). Here, we tested this specifically in elite male volleyball players, who represent an underrepresented sport and a body morphology that is lacking in the literature. The purpose of this investigation is to compare the estimates of currently recommended predictive RMR equations for athletes (Harris-Benedict, Cunningham, Freire, Ten Haaf, and Tinsley) against measured RMR using high-resolution indirect calorimetry in volleyball players. Using a cross-sectional design, 22 international (tier 4) elite male volleyball players underwent evaluations of body composition, RMR, and bloodwork and completed the three-factor eating questionnaire-R18. Participants had a body mass of 93.3 ± 8.7 kg, fat-free mass of 77.5 ± 7.7 kg, and %body fat of 17.0 ± 2.2%. Our main findings were <i>1</i>) the Ten Haaf [-134.9 ± 151 kcal (95% CI)], Freire [-181.4 ± 156 kcal (95% CI)], Harris-Benedict [-256.4 ± 152 kcal (95% CI)], and Cunningham [-299.8 ± 150 kcal (95% CI)] equations under predicted RMR compared with indirect calorimetry (<i>P</i> < 0.05), <i>2</i>) the Tinsley equation was the most accurate [-126.8 ± 150 kcal (95% CI)], but moderately reliable (intraclass correlation coefficient = 0.59), at estimating RMR compared with indirect calorimetry, and <i>3</i>) due to proportional bias toward heavier players, the RMR ratio < 0.90 with the Tinsley equation was not reliable to detect individual volleyball players at greater energy deficit. Future work should explore novel metabolic assessment protocols that will reliably assess energy needs of athletes high in absolute fat-free mass.<b>NEW & NOTEWORTHY</b> The most recently recommended predictive resting metabolic rate equations for athletes are unsuitable for heavier elite male volleyball athletes with higher FFM.