Gut Microbiota as a Regulator of Macronutrient Metabolism, Short-Chain Fatty Acid Synthesis and Inflammatory Response in Athletes from a Sports Medicine Perspective
Abstract
Contest preparation in bodybuilding and fitness combines a high protein intake, restricted carbohydrate and fiber intake, and a sustained energy deficit, and each of these features alters the substrate reaching the colonic microbiota. The objective of this review was to systematize the mechanisms through which the gut microbiota links macronutrient metabolism, short-chain fatty acid synthesis, and the inflammatory response in athletes and to map dietary interventions onto these mechanisms. Peer-reviewed publications from 2021 to 2026 were analyzed in a structured narrative review, with first-hand consulting practice in bodybuilding and fitness as the applied lens. The evidence forms a chain of five links. A diet low in fermentable fiber shifts colonic fermentation toward proteolysis and reduces the butyrate supply to colonocytes, so the epithelial barrier faces peak training load, heat, and dehydration with fewer resources. Increased permeability allows bacterial endotoxin to enter, thereby sustaining systemic inflammation and potentially impeding recovery. Tolerable fiber, cooked vegetables, fermented foods, protein-source switching guided by tolerance, spice polyphenols, hydration and adequate energy availability act on separate links of this chain, with athlete-specific evidence of uneven depth. Strength and physique athletes remain the least studied group. Support of short-chain fatty acid synthesis during contest preparation therefore emerges as a task of sports medicine, and the proposed chain offers a framework for dietary design and for longitudinal research.
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