Long-term effects of advice to consume a high-protein, low-fat diet, rather than a conventional weight-loss diet, in obese adults with Type 2 diabetes: one-year follow-up of a randomised trial

G. D. Brinkworth, M. Noakes, B. Parker, P. Foster, P. M. Clifton

This study compared the long-term weight loss and health outcomes at 1-year follow-up, after a 12-week intensive intervention consisting of two low-fat, weight-loss diets, which differed in protein content. We randomly assigned 66 obese patients (BMI: 27-40 kg/m2) with type 2 diabetes to either a low-protein (15% protein, 55% carbohydrate) or high-protein diet (30% protein, 40% carbohydrate) for 8 weeks of energy restriction (approximately 6.7 MJ/day) and 4 weeks of energy balance. Subjects were asked to maintain the same dietary pattern for a further 12 months of follow-up. The study was completed by 38 of the subjects, with equal dropouts in each group. At Week 64, weight reductions against baseline were -2.2+/-1.1 kg (low protein) and -3.7+/-1.0 kg (high protein), p<0.01, with no diet effect. Fat mass was not different from baseline in either group. At Week 12, both diets reduced systolic and diastolic blood pressure by 6 and 3 mm Hg respectively, but blood pressure increased more with weight regain during follow-up in the low-protein group (p< or =0.04). At Week 64, both diets significantly increased HDL cholesterol and lowered C-reactive protein concentrations. There was no difference in the urinary urea : creatinine ratio at baseline between the two groups, but this ratio increased at Week 12 (in the high-protein group only, p<0.001, diet effect), remaining stable during follow-up in both diets. A high-protein weight-reduction diet may in the long term have a more favourable cardiovascular risk profile than a low-protein diet with similar weight reduction in people with type 2 diabetes.