Introduction: Rapid weight loss and subsequent rapid weight regain (RWR) are common practices in professional mixed martial arts (MMA), driven by weight-category regulations and competitive strategy. Although RWR is often assumed to confer a performance advantage, limited research has examined whether the magnitude of weight regained influences how bouts are won among successful fighters. Methods: This observational study analyzed publicly available regulatory records from Ultimate Fighting Championship and Bellator MMA events sanctioned by the California State Athletic Commission between 2018 and 2024. Only winning fighters were included. Official weigh-in and fight-night body mass were recorded using commission-calibrated scales. RWR was calculated as the percentage change from official weigh-in to fight-night weight. Independent samples t-tests were used to compare RWR by organization and sex division, and one-way analysis of variance was used to examine differences by method of victory. Statistical significance was set at p≤0.05. Results: A total of 154 winning professional MMA fighters were included. Mean RWR was 10.17±3.66%. RWR did not differ significantly between organizations (p=0.147) or between sex divisions (p=0.354). Method of victory was not impacted by RWR, with no significant differences observed between knockout or technical knockout, submission, or decision outcomes (p=0.383). Conclusion: RWR is prevalent among winning professional MMA fighters; however, the magnitude of post-weigh-in weight regain does not appear to influence the method of victory. These findings suggest that while weight regain is a common component of fight preparation, it may not be a determining factor in how competitive success is achieved.
Peacock et al. (Sat,) studied this question.