Dietary patterns for weight and glycemic management in persons with type 1 diabetes: a meta-analysis of clinical trials

Background Medical nutrition therapy is fundamental for managing glycemia and weight in type 1 diabetes, yet dietary guidance specific to this population and relevant subgroups is lacking. Purpose We synthesized the interventional literature investigating diet patterns for glycemic and weight management in youth and adults with type 1 diabetes, with attention to interindividual variation that suggests the need for precision approaches. The protocol was prospectively registered (CRD42024519941). Data Sources AMED, CINAHL, Cochrane Library, Ovid MEDLINE, Ovid Embase, Google Scholar, and Web of Science Core Collection were searched from January 2011 to June 2024. Study Selection Clinical trials ≥4 weeks with ≥10 youth and/or adults diagnosed with type 1 diabetes ≥6 months prior and reported HbA1c or weight were included. Data Synthesis Twelve studies with 668 participants were included. Data were pooled by random-effects models for HbA1c and weight. Studies with insufficient data and subgroup differences were narratively synthesized per Synthesis Without Meta-analysis guidelines. Pooled results of very low to moderate certainty evidence showed no advantage of any particular diet pattern in randomized trials. Very low-quality evidence from single-arm low carbohydrate trials suggested improved HbA1c over time (-0.63% [95%CI –0.99, -0.27]; -6.0 mmol/mol [-10.8, -3.0]). Wide pooled confidence intervals demonstrated between-person heterogeneity; however, stratification of results by participant characteristics was rarely performed. Limitations Limited evidence precluded subgroup analyses to inform precision nutrition approaches. Conclusions Randomized trials are needed to confirm the efficacy of specific diets and determine whether precision nutrition therapies optimize glycemia and weight in persons with type 1 diabetes.