The Diabetes Excess Weight Loss (DEWL) Trial: a randomised controlled trial of high-protein versus high-carbohydrate diets over 2 years in type 2 diabetes

To compare the effectiveness of low-fat high-protein and low-fat high-carbohydrate dietary advice on weight loss, using group-based interventions, among overweight people with type 2 diabetes. Multicentre parallel (1:1) design, blinded randomised controlled trial. Individuals with type 2 diabetes aged 30-75 years and a BMI > 27 kg/m(2) were randomised, by an independent statistician using sequentially numbered sealed envelopes, to be prescribed either a low-fat high-protein (30% of energy as protein, 40% as carbohydrate, 30% as fat) or a low-fat high-carbohydrate (15% of energy as protein, 55% as carbohydrate, 30% as fat) diet. Participants attended 18 group sessions over 12 months. Primary outcomes were change in weight and waist circumference assessed at baseline, 6 and 12 months. Secondary outcomes were body fatness, glycaemic control, lipid profile, blood pressure and renal function. A further assessment was undertaken 12 months after the intervention. Research assessors remained blinded to group allocation throughout. Intention-to-treat analysis was performed. A total of 419 participants were enrolled (mean +/- SD age 58 +/- 9.5 years, BMI 36.6 +/- 6.5 kg/m(2) and HbA(1c) 8.1 +/- 1.2% (65 mmol/mol)). The study was completed by 70% (294/419). No differences between groups were found in change in weight or waist circumference during the intervention phase or the 12-month follow-up. Both groups had lost weight (2-3 kg, p < 0.001) and reduced their waist circumference (2-3 cm, p < 0.001) by 12 months and largely maintained this weight loss for the following 12 months. By 6 months, the difference in self-reported dietary protein between groups was small (1.1% total energy; p < 0.001). No significant differences between groups were found in secondary outcomes: body fatness, HbA(1c), lipids, blood pressure and renal function. There were no important adverse effects. In a 'real-world' setting, prescription of an energy-reduced low-fat diet, with either increased protein or carbohydrate, results in similar modest losses in weight and waist circumference over 2 years. Australia New Zealand Clinical Trials Register ACTRN12606000490572 The Health Research Council of New Zealand (06/337).