Restricted-carbohydrate diets in patients with type 2 diabetes: a meta-analysis.

Many current popular weight-loss diets advocate restricting carbohydrates, but risks and benefits of these diets for patients with diabetes is unclear. We searched for articles published in English between 1980 and April 2006 regarding carbohydrate-restricted diets that included and reported separate results for adult, nonpregnant patients with type 2 diabetes. Articles were limited to studies completed in the United States and Canada. Available data on study design; carbohydrate composition of diet; duration of diet; and the outcomes of weight, lipid levels (total, low-density lipoprotein and high-density lipoprotein cholesterol, and triglycerides), hemoglobin A1c percent and/or fasting glucose were extracted. A total of 56 studies or reviews were evaluated. Thirteen studies met our inclusion criteria. Meta-regression analyses show that hemoglobin A1c, fasting glucose, and some lipid fractions (triglycerides) improved with lower carbohydrate-content diets. Overall effect on weight was equivocal among the studies evaluated in this meta-analysis. Randomized, controlled studies of restricted-carbohydrate diets in patients with diabetes need to be conducted in order to evaluate the overall sustainability of outcomes and long-term safety.