Diets for weight management in adults with type 2 diabetes: an umbrella review of published meta-analyses and systematic review of trials of diets for diabetes remission.
Level 1 - systematic review of randomized trials
Umbrella review and systematic review of randomized controlled trials
PubMed 34796367 · doi:10.1007/s00125-021-05577-2
What was done
Researchers conducted an umbrella review of 19 published meta-analyses of randomized controlled trials (evaluating 2 to 23 primary trials each, n = 100 to 1,587) investigating dietary interventions for weight loss in adults with type 2 diabetes, assessed using AMSTAR 2 and GRADE. Concurrently, they conducted a systematic review of 16 intervention studies evaluating type 2 diabetes remission across different weight-loss dietary strategies, assessed using Cochrane RoB 2, ROBINS-I, and GRADE.
What was found
For weight loss, very low energy diets (400–500 kcal/day for 8–12 weeks) achieved 6.6 kg greater weight loss (95% CI -9.5 to -3.7 kg; GRADE low) than low-energy diets (1,000–1,500 kcal/day). Formula meal replacements led to 2.4 kg greater weight loss over 12–52 weeks (95% CI -3.3 to -1.4 kg; GRADE moderate). Low-carbohydrate diets showed no difference in weight loss compared to higher-carbohydrate/low-fat diets (GRADE high). High-protein, Mediterranean, vegetarian, low-glycaemic-index, and high-monounsaturated-fatty-acid diets showed minimal (0.3–2.0 kg) or no difference versus controls (GRADE very low to moderate). For type 2 diabetes remission at 1 year, programs using an initial low-energy total diet replacement achieved a median remission rate of 54% (GRADE high). Remission rates were 11% for meal replacements, 15% for Mediterranean diets (GRADE moderate/low), 20% for ketogenic/very low-carbohydrate diets, and 22% for very low-energy food-based diets (both GRADE very low).
Why it matters
Weight reduction and diabetes remission are driven by the magnitude of energy restriction and structured total diet replacement rather than specific macronutrient profiles.
Limits
Twelve of the 19 included meta-analyses were judged low or critically low quality by AMSTAR 2. Evidence for diabetes remission with ketogenic, very low-carbohydrate, and food-based very low-energy diets was at serious or critical risk of bias. Most studies followed participants for one year or less, leaving long-term maintenance, vascular complications, and clinical endpoints unmeasured.
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