PREVIEW - Results from a 3-year randomised 2 x 2 factorial multinational trial investigating the role of protein, glycemic index and physical activity for prevention of type-2 diabetes.

AIM To compare the impact of 2 long-term weight-maintenance diets: High-protein (HP), low-glycaemic index (GI) and moderate-protein (MP), moderate-GI, combined with high-intensity (HI) or moderate-intensity (MI) physical activity (PA) on incidence of type-2 diabetes (T2D) after rapid weight loss. MATERIALS AND METHODS A 3-year multicentre randomised trial in 8 countries using a 2x2 diet-by-PA factorial design. 8-weeks weight-reduction was followed by a 3-year randomised weight-maintenance phase. 2,326 adults (25-70 y, BMI≥25 kg/m2 ) with pre-diabetes were enrolled. Primary endpoint was 3-year incidence of T2D analysed by diet treatment. Secondary outcomes included glucose, insulin, HbA1C, and body weight. RESULTS Total number of T2D cases was 62 and cumulative incidence rate 3.1%, with no significant differences between the 2 diets, PA, or their combination. T2D incidence was similar across intervention centres, irrespective of attrition. Signficantly fewer achieved normo-glycemia in the HP compared with the MP group (p<0.0001). At 3-years, normoglycemia was lowest in HP-HI (11.9%) compared with the other 3 groups (20.0-21.0%, p<0.05). There were no group differences in body weight change (-11% after 8-weeks weight reduction; -5% after 3 years weight maintenance) or in other secondary outcomes. CONCLUSIONS Three-year incidence of T2D was much lower than predicted and did not differ between diets, PA or their combination. Maintaining the target intakes of protein and GI over 3 years was difficult, but the overall protocol combining weight loss, healthy eating, and physical activity was successful in markedly reducing the risk of T2D. This is an important clinically relevant outcome. This article is protected by copyright. All rights reserved.