Role of Nutrition Therapy in Prediabetes: A Systematic Review

Prediabetes represents a critical window for diabetes intervention, but the comparative effectiveness of dietary strategies remains uncertain. This systematic narrative review evaluated structured dietary interventions (SDIs) on metabolic outcomes in adults with prediabetes and identified approaches that may support glycemic improvement and diabetes prevention. PubMed, Embase, the Cochrane Library, and Web of Science were searched for randomized controlled trials (RCTs) published through August 23, 2025. Eligible studies compared SDIs with comparators in adults with prediabetes; observational and nonrandomized trials were excluded. Risk-of-bias (RoB) was assessed using the Cochrane RoB 2 tool. Because of substantial heterogeneity in interventions, comparators, follow-up, and outcomes, findings were synthesized narratively. Finally, ten RCTs, involving 1,098 participants, were included. At 12－52 weeks, calorie-restricted and low-carbohydrate diets were associated with reductions in body weight and glycemic indices, with some trials reporting normoglycemia. Diets for low-glycemic-index appeared to improve insulin sensitivity, whereas Mediterranean diets improved fasting glucose and ectopic fat. High-protein, low-glycemic-index diets may sustain longer-term metabolic enhancements. Intermittent fasting, particularly alternate-day fasting, appeared beneficial for selected outcomes, including weight loss, with glycemic advancements in a few studies. However, interpretation is limited by the small number of trials, heterogeneity, and RoB concerns. Overall, SDIs may offer metabolic benefits for adults with prediabetes, but no single strategy emerged as universally optimal. These findings provide evidence-informed dietary considerations, and further high-quality trials are needed to strengthen sustainable diabetes prevention strategies.