A comparison of rapid weight loss practices within combat sport athletes subjected to <24 hour vs ≥24 hour competition weigh-ins

• In-person sampling approach ensuring responses received from the targeted population. • ≥24 h weigh-in athletes had higher prevalence and magnitude of body mass loss (8 13 %). • More extreme RWL methods & higher RWL scores (43.8 vs 28.2) in ≥24 h weigh-in athletes. • First study comparing RWL practices of. This study aimed to compare the rapid weight loss (RWL) practices of combat athletes ( n = 35, male n = 30, female n = 5) from Great Britain subjected to <24 hour ‘<24h’ versus ≥24 hour ‘≥24h’ competition weigh-ins. The previously validated ‘Rapid Weight Loss Questionnaire’ established RWL practices. Of total responses, 31/35 (88.6 %) surveyed had reduced body mass to compete, (‘<24h’; 20 of 24, 83.3 %. ‘≥24h’; 11 of 11, 100 %). The ‘≥24h’ group attributed a significantly greater ( p < 0.01) ‘habitual’ (9.7 % vs 5.2 %) and ‘highest’ (13.0 % vs 8.7 %) pre-competition body mass loss and post competition body mass gain (9.4 % vs 3.9 %) compared to ‘<24h’. The RWL score was significantly higher for the ‘≥24h’ group compared to the ‘<24h’ group (43.8 vs 28.2, p < 0.001). For the total cohort, ‘gradual dieting’ (61.3 %), ‘increased exercise (45.2 %), ‘restricting fluid ingestion’ (38.7 %) and ‘hot water immersion’ (32.3 %) were RWL methods most commonly ‘always’ used. Prevalence of RWL is high amongst competitive UK combat athletes and performed by all surveyed ≥24 h group athletes. Magnitude of RWL was significantly greater in ≥24 h group athletes, with athletes experiencing body mass loss levels (∼8–13 %) which are concerning from a health and performance perspective.