Low-Fat Diet and Risk of Treated Diabetes Mellitus

Type 2 diabetes continues to rise in the United States. In women, this form of diabetes rises after menopause. By the time that women and men are in their 70s, more women will have diabetes than will men. The toll on health is that type 2 diabetes can increase the risk of heart disease, reduce well-being, and shorten one’s life. Fortunately, there are lifestyle changes that can reduce the risk of developing diabetes. Research from the Diabetes Prevention Study in the United States (funded by the National Institutes of Health) showed that modest weight loss and exercise with a low-fat diet may reduce the onset of diabetes in persons who are at risk of developing diabetes.

In the WHI Dietary Modification Trial (Dietary Study), after an average of 8.1 years of follow-up, a total of 3,342 of the 48,835 participants developed diabetes mellitus that was treated by insulin or medications. There was a 4% reduced risk (not statistically significant) of developing diabetes in the low-fat dietary change group compared to participants in the usual diet comparison group. The low-fat dietary change group was asked to reduce their fat intake to 20% of energy and to increase their vegetable and fruit intake to five or more daily servings and grains to six or more daily servings.

Participants who reported greater reductions in fat intake after the first year had greater reductions in risk of diabetes (statistically significant). However, the trend of reduced risk was not statistically significant after accounting for weight loss. Participants in the dietary change group lost nearly five pounds after the first year and maintained a lower weight than the comparison group throughout the study. Thus modest weight loss, rather than the proportion of fat, carbohydrate, and protein in the diet, may be the dominant predictor of reducing the risk of developing diabetes. Modest weight loss is typical when following a low-fat dietary pattern that is rich in vegetables, fruits, and grains.

Although the risk of developing diabetes did not decrease, neither did risk increase. A benefit of a low-fat dietary pattern that includes lots of vegetables and fruits and grains is that it is sustainable. After an average of 7 years of follow-up, participants in the low-fat dietary change intervention group maintained a significantly lower fat intake (and minor weight loss) than did participants in the usual diet comparison group. This supports a low-fat dietary eating style that has lots of vegetables, fruits, and grains, as an option for postmenopausal women who are concerned about developing diabetes.