Diet Quality, Weight Loss, and Diabetes Incidence in the Diabetes Prevention Program

Background: We evaluated whether diet quality is a predictor of weight loss and reduced diabetes risk, independent of caloric intake in the Diabetes Prevention Program (DPP) cohort, a randomized clinical trial of adults at risk for diabetes. Methods: This secondary analysis included 2914 participants with available data (964 intensive lifestyle (ILS), 977 metformin, 973 placebo). Dietary intake was assessed using a 117-item food frequency questionnaire. Diet quality was quantified using the Alternative Healthy Eating Index 2010 (AHEI). AHEI ranges from 0 to 110, with higher scores corresponding to higher quality diets. ILS participants had greater improvement (p<0.001) in AHEI over 1-year (4.2±9.0) compared to metformin (1.2±8.5) and placebo (1.4±8.4). We examined the association between AHEI change and weight change from baseline to 1-year using linear regression, and that between 1-year AHEI change and incident diabetes, using hazard models over an average 3 years follow-up. Models were evaluated within treatment group and adjusted for relevant characteristics including caloric intake, physical activity, BMI and AHEI. Models testing incident diabetes were further adjusted for baseline fasting and 2h glucose. Results: An increase in AHEI score was associated with weight loss in ILS [β per 10-point increase (SE) -1.2kg (0.3, p<0.001)], metformin [-0. 90kg (0.2, p<0.001)] and placebo [-0.55kg (0.2, p=0.01)]. However, AHEI change was not associated with incident diabetes in any group before or after adjustment for weight change. Conclusions: Controlling for weight, diet quality was not associated with diabetes incidence but helps achieve weight loss, an important factor in diabetes prevention.