High protein weight loss diets in obese subjects with type 2 diabetes mellitus

Background and aim: Diets where carbohydrate has been partially exchanged for protein have shown beneficial changes in persons with type 2 diabetes but no studies have enrolled people with albuminuria. We aim to determine if a high protein to carbohydrate ratio (HPD) in an energy reduced diet has a beneficial effect on metabolic control and cardiovascular risk factors without negatively affecting renal function. Method and results: Adult, overweight participants with type 2 diabetes, with albuminuria (30-600mg/24h or an albumin-to-creatinine ratio of 3.0-60mg/mmol), and estimated GFR of >40ml/min/1.73m² were enrolled. Participants were randomized to an HPD or an SPD. Protein:fat:carbohydrate ratio was 30:30:40% of energy for the HPD and 20:30:50% for the SPD. Main outcomes were renal function, weight loss, blood pressure, serum lipids and glycaemic control. We recruited 76 volunteers and 45 (35 men and 10 women) finished. There were no overall changes in renal function at 12 months and no significant differences in weight loss between groups (9.7±2.9kg and 6.6±1.4kg HPD and SPD group respectively; p=0.32). Fasting blood glucose decreased significantly with no treatment effect. The decrease in HbA1c differed between treatments at 6 months (HPD -0.9 vs. SPD -0.3%; p=0.039) but not at 12 months. HDL increased significantly with no treatment effects. There were no changes in LDL or blood pressure overall but DBP was lower in the HPD group (p=0.024) at 12 months. Conclusion: Weight loss improved overall metabolic control in this group of well controlled participants with type 2 diabetes regardless of diet composition.