A Low-Fat Dietary Pattern and Diabetes: A Secondary Analysis From the Women’s Health Initiative Dietary Modification Trial

ObjectiveWe performed a secondary analysis to evaluate the effect of the Women's Health Initiative dietary intervention on incident diabetes and diabetes treatment in postmenopausal women.Research design and methodsA total of 48,835 women were randomized to a comparison group or an intervention group that underwent a behavioral/nutritional modification program to decrease fat and increase vegetable, fruit, and grain intake for an average of 8.1 years. Ninety-three percent of participants completed the intervention, and 71% participated in active follow-up through 30 September 2015 (median 17.3 years). We measured time to development of treated diabetes and progression from oral antihyperglycemic agents to insulin. Serum glucose and insulin were measured in a subsample of women (N = 2,324) at baseline and years 1, 3, and 6.ResultsDuring the trial, intervention group women had lower rates of initiation of insulin therapy (hazard ratio [HR] 0.74 [95% CI 0.59, 0.94]; P = 0.01). Moreover, women with baseline waist circumference ≥88 cm (P interaction = 0.01) and worse metabolic syndrome scores (P interaction = 0.02) had the greatest reduction in risk of initiating insulin therapy. The decreased risk from the intervention was present during the cumulative follow-up (HR 0.88 [95% CI 0.78, 0.99]; P = 0.04). In participants with measured biomarkers (5.8% subsample) who had baseline glucose <100 mg/dL, the intervention reduced the risk of developing glucose ≥100 mg/dL by 25% (odds ratio 0.75 [95% CI 0.61, 0.93]; P = 0.008). Adjustment for weight change did not alter the results.ConclusionsIn this secondary analysis, a dietary intervention in postmenopausal women aimed at reducing fat and increasing intake of vegetables, fruits, and grains did not increase risk of diabetes and may have slowed progression