Prevention of type 2 diabetes mellitus by changes in diet among subjects with abnormal glucose metabolism: a randomized clinical trial

Previous studies demonstrated that changes in lifestyle slow the progression of impaired glucose tolerance to overt diabetes but few trials examined the effect of diet alone without weight loss on the prevention of diabetes. We investigated the efficacy of two types of diet with different macronutrients, on preventing or delaying the onset of type 2 diabetes in subjects with either impaired fasting glucose or impaired glucose tolerance. Three hundred and twenty-two subjects with prediabetes were randomly assigned to a high monounsaturated fat diet, normal fat diet, or control groups and followed for 2 years. For calculating the daily energy requirement in subjects with BMI >= 25 kg/m(2), the weight was adjusted with the use of 110 of the ideal body weight with no attempt for losing body weight. There was no difference in body weight decrease among the three groups after 2 years. The cumulative incidence of diabetes was 9.3 (95 CI, 3.6-14) in the high monounsaturated fat diet (HMD) group, 13.2 (95 CI, 6.4-19) in the normal fat diet (NFD) group, and 18.3 (95 CI, 10-25) in the control group. The cumulative incidence of diabetes was 57 lower in the HMD group than that in the control group (95 CI, 0.1-0.9; P = 0.03). This value was not significant in the NFD group (RR, 0.60; 95 CI, 0.2-1.2; P = 0.1). Type 2 diabetes can be prevented by a high-monounsaturated fat, low-carbohydrate diet and receiving energy based on the adjusted ideal body weight without a weight loss program. Trial registration number: NCT02250066