A network meta-analysis of the comparative efficacy of different dietary approaches on glycaemic control and weight loss in patients with type 2 diabetes mellitus and overweight or obesity.

Background: Despite considerable literature supporting the benefit of dietary interventions in individuals with type 2 diabetes mellitus (T2DM) and overweight/obesity, which diet works best is currently unknown. We conducted a systematic review and network meta-analysis (NMA) to evaluate the comparative effectiveness of different dietary approaches in overweight or obese adults with T2DM. Methods: We searched EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL) and PubMed up till July 2023 for controlled studies using different dietary approaches. Next, we updated the literature search to September 2024 but found no new relevant studies. Glycated hemoglobin A1c (HbA1c) levels and body weight were used as primary outcomes. For each outcome, a pooled effect was determined for each intervention compared with other interventions. Mean differences (MDs) and 95% confidence intervals (95% CIs) were computed. The surface under the cumulative ranking curve (SUCRA) was used for ranking the dietary approaches. Moreover, confidence was assessed using the CINeMA (confidence in network meta-analysis) framework. Results: Overall, 31 trials that compared eight diet interventions (Mediterranean, moderate-carbohydrate, low-carbohydrate, vegetarian, low-glycaemic index/load, low-fat, high-protein and control diets) and involved 3096 people were included. In terms of glycemic control, the Mediterranean diet yielded the best ranking (SUCRA: 88.15%), followed by the moderate-carbohydrate diet (SUCRA: 83.3%) and low-carbohydrate (LC) diet (SUCRA: 55.7%). In terms of anthropometric measurements, the LC diet (SUCRA: 74.6%) ranked first, followed by the moderate-carbohydrate diet (SUCRA: 68.7%) and vegetarian diet (SUCRA: 57%). These results also showed that the differences in almost all dietary patterns regarding anthropometric measurements were mostly small and often trivial. Conclusions: In summary, the Mediterranean diet was the most efficient dietary intervention for the improvement of glycaemic control, and the LC diet obtained the highest score for anthropometric measurements in individuals with T2DM and concurrent overweight/obesity.