This study investigated nutrition, hydration, supplementation, and body composition in relation to performance among mixed martial arts athletes practicing rapid weight loss. Mixed martial arts athletes practice intentional dehydration and nutritional fasting to achieve rapid weight loss, a practice that can damage health and performance. Male mixed martial arts athletes practicing rapid weight loss participated in the study during a week of competition which was not the same for all athletes. Food/activity journals were collected to assess nutrition, fasting, and supplementation. Urine specific gravity was assessed at baseline, weigh-ins, and endpoint. Body composition and punch velocity were assessed at baseline and endpoint. Competition result and self-rated performance data were also recorded. Descriptive statistics, Pearson correlations, ANOVA, and t-tests were utilized to determine the significance of relationships between variables. Of the participants who completed the study, eight (88.9%) were dehydrated at the official weigh-ins to qualify for competition, with one (11.1%) failing to achieve euhydration prior to competition. Among the sample of nine mixed martial arts athletes, significant weight loss was observed (M=14.54 lb, SD=4.21 lb). Changes in punching velocity were negatively correlated with fasting duration (r=-0.763, p\u3c.05). Self-rated performance was positively correlated with changes in punching velocity (r=0.676, p\u3c.05) and negatively correlated with endpoint USG (r=-0.678, p\u3c.05). These findings suggest shorter fasting periods may be beneficial to combat sports athletes practicing rapid weight loss. However, a study of these factors across a larger sample is warranted before drawing definitive conclusions
