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

Abstract

Objective: We 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 methods: A 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.

Results: During 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.

Conclusions: In 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.

Trial registration: ClinicalTrials.gov NCT00000611.

© 2017 by the American Diabetes Association.

Figures

Figure 1

Diabetes outcomes during the WHI DMT. A: Diabetes progression for the DMT participants, exclusive of women with diabetes at randomization. The reduced risk for insulin initiation, from randomization to first report of insulin, for intervention-group women (T2, HR 0.74) is shown in the component outcomes: T1, time from randomization to first report of pills for diabetes (HR 0.95), and T3, time from pills to first report of insulin (HR 0.82). B: Progression from oral agents to insulin for DMT participants with diabetes and taking oral agents at baseline.

Figure 2

Subgroup analysis for the time from randomization to first report of insulin use (T2) during the WHI DMT in women without diabetes at randomization. BP, blood pressure; C, comparison; I, intervention; wk, week. *Statistical significance of subgroups is based on a test of the interaction between subgroup and randomization group. For the subgroups of age, BMI, physical activity, blood pressure/hypertension, and metabolic syndrome score, a 1-degree-of-freedom trend test of the interaction was used. †Score ranges from 0 (best) to 3 (worst) and is a sum of these binary components: waist circumference ≥88 cm, high cholesterol requiring pills, or blood pressure >130/85 mmHg (or ever treated for hypertension).