Effects of high-protein diets on body weight, glycaemic control, blood lipids and blood pressure in type 2 diabetes: meta-analysis of randomised controlled trials

High-protein diets are popular for weight management, but the health effects of such diets in diabetic persons are inconclusive. The aim of the present meta-analysis was to examine the effects of high-protein diets on body weight and metabolic risk factors in patients with type 2 diabetes. We searched the PubMed and Cochrane Library databases for relevant randomised trials up to August 2012. Either a fixed-or a random-effects model was used to combine the net changes in each outcome from baseline to the end of the intervention. Overall, nine trials including a total of 418 diabetic patients met our inclusion criteria. The study duration ranged from 4 to 24 weeks. The actual intake of dietary protein ranged from 25 to 32% of total energy in the intervention groups and from 15 to 20% in the control groups. Compared with the control diets, high-protein diets resulted in more weight loss (pooled mean difference: -2.08, 95% CI -3.25, -0.90 kg). High-protein diets significantly decreased glycated Hb A(1C) (HbA(1C)) levels by 0.52 (95% CI -0.90, -0.14) %, but did not affect the fasting blood glucose levels. There were no differences in lipid profiles. The pooled net changes in systolic and diastolic blood pressure were -3.13 (95% CI -6.58, 0.32) mmHg and -1.86 (95% CI -4.26, 0.56) mmHg, respectively. However, two studies reported a large influence on weight loss and HbA(1C) levels, respectively. In summary, high-protein diets (within 6 months) may have some beneficial effects on weight loss, HbA(1C) levels and blood pressure in patients with type 2 diabetes. However, further investigations are still required to draw a conclusion.