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Long-term low-fat diet does not increase diabetes risk in postmenopausal women

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January 3, 2018

Barbara V. Howard
Barbara V. Howard

Postmenopausal women without diabetes assigned to a dietary intervention to decrease fat and increase vegetable, fruit and grain consumption were not at increased risk for diabetes and progression to the disease may have slowed compared with those who received printed health-related materials, according to findings from a secondary analysis of the Women’s Health Initiative.

Barbara V. Howard, PhD, senior scientist and former president of MedStar Health Research Institute in Hyattsville, Maryland, and professor of medicine at Georgetown University School of Medicine, and colleagues evaluated data from WHI on 48,835 postmenopausal women with or without diabetes randomly assigned to an intervention group that underwent a behavioral/nutritional modification program to decrease fat and increase vegetable, fruit and grain intake or to a control group that received printed health-related materials during a mean of 8.1 years.

Researchers sought to determine the effect of the dietary intervention on incident diabetes and diabetes treatment. Follow-up was a median of 17.3 years.

A subsample of 2,324 participants were evaluated for serum glucose and insulin measurements at baseline and years 1, 3 and 6.

Overall, 45,579 participants did not have diabetes at baseline with 18,250 assigned to the intervention group (mean age, 62.1 years) and 27,329 assigned to the control group (mean age, 62.2 years); 1,444 participants had diabetes at baseline with 564 assigned to the intervention group (mean age, 63.8 years) and 880 assigned to the control group (mean age, 63.7 years).

During the trial, participants without diabetes at baseline assigned to the dietary intervention were less likely to initiate insulin therapy (HR = 0.74; 95% CI, 0.59-0.94), had reduced rates of oral therapy initiation (HR = 0.95; 95% CI, 0.88-1.02) and less progression from oral agents to insulin (HR = 0.82; 95% CI, 0.64-1.04) compared with the control group. The risk for insulin use did not differ between the two groups in those using oral diabetes agents at baseline.

The risk for initiating insulin therapy in those without diabetes at baseline was lowest among participants with a baseline waist circumference at least 88 cm (P = .01 for interaction) and worse metabolic syndrome scores (each increase in the number of components at baseline; P = .02 for interaction) compared with their counterparts.

Among the subsample without diabetes with available serum glucose and insulin measurements, a 2% lower mean glucose level was observed in those assigned to the intervention group compared with the control group (94.9 mg/dL vs. 96.3 mg/dL; P < .001). Among those with glucose level less than 100 mg/dL at baseline, the risk for developing a glucose level more than 100 mg/dL was 25% lower in the intervention group compared with the control group (OR = 0.75; 95% CI, 0.61-0.93).

“Since weight control or loss is paramount in management of type 2 diabetes, our results show that long-term use of a low-fat diet does not worsen diabetes. In fact, it slows progression to insulin therapy and progression to diabetes in those at risk for diabetes,” Howard told Endocrine Today.

“We plan to determine which of the several dietary changes — which fat or whether increases in vegetables or grains — had more impact,” she said. “More long-term, large diet studies are needed. Too much of current nutrition strategy is based on small studies of selected individuals.” – by Amber Cox

For more information:

Barbara V. Howard, PhD, can be reached at barbara.v.howard@medstar.net.

Disclosures: The authors report no relevant financial disclosures.