The Effects of Dietary Fiber and High-Dietary-Fiber Diets on Body Weight Regulation and Lipid Metabolism in Athletes: A Narrative Review.

The beneficial effects of dietary fiber (DF) and high-dietary-fiber diets (high-DF diets) on body weight (BW) regulation and lipid metabolism have been extensively investigated in the general population. However, due to the unique metabolic adaptations of athletes, exercise-specific nutritional requirements, and enhanced gastrointestinal sensitivity caused by intensive training and competition, the evidence for their application and in-depth mechanism remains limited. This review synthesizes current evidence on the effects of DF and high-DF diets on BW regulation and lipid metabolism in athletic populations. Emerging data indicate that athletes exhibit unique lipid metabolic phenotypes and gut microbial compositions relative to non-athletic individuals-factors that may modulate their physiological responses to DF interventions. Studies conducted specifically in athletes suggest that DF supplementation and high-DF diets-including the vegetarian diet and the Mediterranean diet-may support favorable changes in body composition and lipid-related biomarkers. Nevertheless, these benefits appear to be moderated by sport discipline, biological sex, and interindividual variability in metabolic and gastrointestinal physiology. Critically, excessive or poorly timed DF intake-particularly during intense training blocks or immediately before or during competition-may exacerbate gastrointestinal discomfort and impair energy availability, thereby potentially compromising performance. Consequently, the integration of DF into athletic nutrition strategies necessitates individualized consideration of fiber type, dosage, timing of ingestion, fermentability, and gastrointestinal tolerance. Future research should prioritize rigorously designed longitudinal studies and randomized controlled trials employing standardized DF interventions and outcome assessments. Comprehensive evaluation-including metabolic parameters, markers of energy availability, gastrointestinal symptomatology, and microbiome profiling-will be essential to inform evidence-based, personalized DF recommendations aligned with athletes' training phases and metabolic profiles.