Effects of Weight-Cutting Practices on Sleep, Recovery, and Injury in Combat Sports: A Scoping Review

Objectives: This scoping review aims to synthesize the methodological characteristics of weight-cutting strategies, summarize their effects on sleep, recovery, and injury outcomes, and identify research gaps. Methods: Following the PRISMA guidelines, searches were conducted on 20 May 2025, across PubMed, Scopus, and Web of Science, with snowball citation tracking and expert consultation to enhance retrieval. Inclusion criteria targeted peer-reviewed studies involving competitive or recreational combat sport athletes (all ages and sexes) undergoing weight-cutting practices, reporting outcomes on sleep (e.g., quality and duration), recovery (e.g., perceived fatigue and biomarkers), or injury incidence (e.g., reported injuries and odds ratios). Studies included randomized controlled trials, non-randomized trials, or cohort studies with or without comparator groups. The risk of bias was assessed using the RoB 2 tool for randomized trials and the ROBINS-I tool for non-randomized studies. Results: From 2784 records, 17 studies met the inclusion criteria. Participant ages ranged from 17.79 ± 0.75 to 30.1 ± 7.5 years, predominantly national-level combat sport athletes (wrestling, judo, taekwondo, and MMA). Rapid weight loss (RWL, 2-10% body mass loss over 1-7 days) via food/fluid restriction, sauna use, and caloric deficits consistently increased creatine kinase (peaking at 713.4 ± 194.6 U/L), perceived fatigue (41.8 ± 0.9 to 51.3 ± 2.0 A.U.), and injury rates (45.62 injuries/1000 athletic exposures in females). Cortisol responses showed increases in some studies (from 499.9 ± 107.8 to 731.6 ± 80.2 nmol/L) and decreases in others (from 603.2 ± 146.8 to 505.8 ± 118.4 nmol/L). Sleep quality showed mild worsening (5.15 ± 1.83 to 5.52 ± 1.71 A.U.), and perceived recovery declined post-RWL (101.40 ± 2.52 to 87.63 ± 2.47 A.U.). Conclusions: RWL in combat sports consistently impairs recovery, increases muscle damage and fatigue, and increases injury risk, though sleep quality effects are less pronounced. Variability in weight-cutting protocols, outcome measures, and study designs shows the need for standardized methodologies, broader inclusion of female athletes, and longitudinal studies to assess long-term impacts.