Medical Nutrition Therapy and Weight Loss Questions for the Evidence Analysis Library Prevention of Type 2 Diabetes Project: Systematic Reviews

Background: Eleven recommendations, based on systematic reviews, were developed for the Evidence Analysis Library's prevention of type 2 diabetes project. Two recommendations, medical nutrition therapy (MNT) and weight loss, were rated strong.

Objective: Present the basis of systematic reviews for MNT and weight loss recommendations.

Methods: Literature searches using Medline were conducted to identify studies that met eligibility criteria. The MNT literature search covered a time span of 1995 to 2012, the weight loss literature search covered 2008 to 2012 due to inclusion of a Cochrane Review meta-analysis of randomized controlled trials (RCTs) published in 2008. Eligibility criteria for inclusion of articles included original research using higher-quality study designs (ie, RCTs, case control, cohort, crossover, and nonrandomized trials) with participants aged >18 years and meeting prediabetes or metabolic syndrome diagnostic criteria. MNT was defined as individualized and delivered by a registered dietitian nutritionist or international equivalent and length of weight loss interventions was ≥3 months.

Main outcome measures: Two-hour postprandial blood glucose level, glycated hemoglobin level, albumin-to-creatinine ratio (metabolic syndrome samples only), fasting blood glucose level, high-density lipoprotein cholesterol level, systolic and diastolic blood pressure, triglyceride levels, urinary albumin excretion rate (metabolic syndrome samples only), waist circumference (WC), and waist-to-hip ratio were evaluated.

Results: For MNT, 11 publications were included, with all 11 using an RCT study design and 10 including participants with prediabetes. A majority of publications reported significant improvements in glycemic outcomes, WC, and blood pressure. For weight loss, 28 publications were identified, with one meta-analysis (only included RCTs) and 20 publications using an RCT study design, with the meta-analysis and 10 RCTs including participants with prediabetes. A majority of publications reported significant improvements in glycemic outcomes, triglyceride level, WC, and blood pressure.

Conclusions: Systematic reviews provided strong evidence that MNT and weight loss alter clinical parameters in ways that should reduce the risk of developing type 2 diabetes.