Effect of Modulation of Gut Microbiota through Dietary Interventions on Metabolic Health Indicators

The human gastrointestinal tract harbors a complex and diverse community of microorganisms, collectively referred to as the gut microbiota. This ecosystem, composed of bacteria, archaea, viruses, and fungi, plays a critical role in host health by contributing to digestion, nutrient absorption, immune function, and metabolic regulation. In recent years, research has increasingly highlighted the link between gut microbiota composition and metabolic disorders such as obesity, type 2 diabetes mellitus (T2DM), dyslipidemia, metabolic syndrome, and non-alcoholic fatty liver disease (NAFLD). Dysbiosi, which is an imbalance in the microbial community, has been implicated in the pathogenesis and progression of these conditions. Dietary interventions aimed at modulating the gut microbiota have emerged as promising strategies for managing and potentially reversing metabolic disorders. This systematic review evaluates the current evidence on the effects of various dietary interventions such as the Mediterranean diet, ketogenic diet, low-fat vegan diet, low-carbohydrate diet, and supplementation with probiotics, prebiotics, and synbiotics on gut microbiota composition and key metabolic indicators in adults with metabolic disorders. Following PRISMA guidelines and the PICO framework, fifteen randomized controlled trials and crossover studies published between 2010 and 2025 were reviewed. These studies involved 1669 adult participants diagnosed with metabolic disorders and assessed changes in microbiota composition alongside metabolic outcomes including body weight, insulin sensitivity, blood glucose, lipid profiles, and inflammatory biomarkers. Findings across the studies demonstrated that dietary interventions frequently resulted in positive shifts in gut microbial communities. In particular, increased abundance of beneficial taxa such as Bifidobacterium, Faecalibacterium prausnitzii, and Akkermansia muciniphila was often associated with improved metabolic outcomes. These bacteria are known to produce short-chain fatty acids (SCFAs), especially butyrate, which support gut barrier function, reduce inflammation, enhance insulin sensitivity, and regulate lipid metabolism. Several studies reported significant reductions in body weight, visceral fat, and BMI, as well as improvements in fasting glucose, HbA1c, cholesterol levels, and inflammatory cytokines following dietary intervention. However, the review also identified variability in individual responses and outcomes across studies. Factors such as baseline gut microbiota composition, genetic predisposition, type and duration of dietary intervention, and adherence influenced results. Not all studies reported statistically significant improvements, and some control groups also experienced metabolic benefits, limiting the observed differences.