Different Patterns of Rapid Weight Loss in National-Team Judo and Muay Thai Athletes: Magnitude, Frequency, Methods, and Sources of Influence

Background: Rapid weight loss (RWL) is common in weight-class sports, but its magnitude, frequency, methods, and social determinants may differ between disciplines. This study characterized RWL practices among national-team judo and Muay Thai athletes and explored differences between sports. Hypothesis: RWL patterns would differ between judo and Muay Thai, particularly in magnitude, frequency, methods, and sources of influence. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: A total of 25 adult national-team athletes (11 judo, 14 Muay Thai) completed the Rapid Weight Loss Questionnaire (RWLQ). We summarized prevalence, magnitude, frequency, duration, age at onset, postcompetition weight regain, weight-loss methods, and perceived sources of influence. The primary RWLQ score was evaluable for 23 athletes. Between-sport comparisons used Fisher exact tests and permutation-based Wilcoxon rank-sum tests; Benjamini-Hochberg adjustment was used for method-use and influence-score comparison families. Results: Previous RWL was reported by 24 of 25 athletes (96.0%). Among athletes with previous RWL, the median number of episodes in the previous year was 3.5 (interquartile range [IQR], 1.0-10.5). Habitual loss was 6.8% of usual body mass (IQR, 3.9%-8.3%; n = 22). Dehydration-related methods were reported by 22 of 24 (91.7%) and fasting or skipping meals by 18 of 24 (75.0%) participants. Annual episodes were higher in judo (median, 10.0 vs 2.0; P = 0.02), whereas habitual loss was higher in Muay Thai (6.9% vs 4.5%; P = 0.11). Among 23 athletes with evaluable primary RWLQ scores, the medians were 40.0 in judo and 34.0 in Muay Thai ( P = 0.19). Coaches were the most frequently reported influence (20 of 24; 83.3%). Conclusion: RWL was common in this sample and frequently involved dehydration-related practices and food restriction. Exploratory comparisons suggested differences in the frequency and magnitude of weight loss between sports, but the small sample and imbalance in sex distribution limit sport-specific inference. Clinical Relevance: Multidimensional assessment should consider the athlete’s wider sporting environment.