Body Composition and Dietary Intake of Combat Sports Athletes: A Systematic Review

Background/Objectives: Combat sports are characterised by successive high-intensity and short-duration episodes (rounds) interspersed with short rest periods (intermittent nature). Athletes’ body composition and dietary intake are closely related to physiological demands, and they are determining factors in athletic performance. The aim of this systematic review was to describe the body composition, dietary intake, and food habits of male and female combat sports athletes, and to verify whether they met nutritional recommendations. Methods: A search was performed in the PubMed, Web of Science, and Scopus databases following the PRISMA statement. The timeframe for the search included studies from the year 2000 until 2 February 2026. Risk of bias was assessed using the STROBE and the Newcastle–Ottawa checklists. Initially, 328 documents were identified. The research focused on amateur, semi-professional, or professional athletes in boxing, karate, kickboxing, jiu-jitsu, taekwondo, judo, muay thai, and mixed martial arts (MMA). Results: After screening, 23 studies met the inclusion criteria and were included in the review. Most of the athletes, both men and women, had normal body mass indices (BMIs), with low or normal fat percentages and adequate muscle mass during both reference and pre-competitive periods. Regarding dietary intake, most of the athletes, male and female, had energy and carbohydrate intakes below official recommendations. Energy and nutrient intake decreased during pre-competition periods as a strategy for achieving pre-competitive rapid weight loss, which mainly occurred at the expense of lean mass. Conclusions: Despite maintaining adequate body composition, combat sports athletes reported an inadequate dietary pattern, especially during pre-competitive periods, which may negatively affect athletic performance.