Low-Carb Diet Linked to Insulin Resistance in Gestational Diabetes
Current dietary practice for women who have gestational diabetes is to focus on a low-carbohydrate diet, which often coincides with increased fat consumption. But low-carbohydrate, high-fat diets may increase maternal insulin resistance and infant adiposity, according to preliminary findings of a study presented by Teri L. Hernandez, PhD, RN, assistant professor of medicine and nursing at the University of Colorado.
In the small trial, 11 pregnant women with gestational diabetes were randomized to either a low-carbohydrate, high-fat diet (LC/HF) or a high-carbohydrate, low-fat diet (HC/LF). The LC/HF was comprised of 40% carbohydrate, 45% fat, and 15% fat, while the HC/LF diet was comprised of 60% carbohydrate, 25% fat, and 15% protein. In both diets, 82% of the carbohydrates were complex. All meals were provided by the researchers.
The researchers took blood samples at 30-32, and 37 weeks into the women’s pregnancies and biopsied the women’s adipose tissue at 37 weeks. At 37 weeks the women in the LC/HF group had higher fasting blood glucose (P = 0.007), insulin (P = 0.06), maternal insulin resistance (P = 0.02), and post-prandial free fatty acids (P = 0.037) than those in the HC/HF group. Mean adiposity was greater in infants born to mothers in the LC/HF group, at 14% compared to 11% in infants born to mothers in the HC/LF group. Overall, the higher fasting insulin and insulin resistance among women in the LC/HF group was associated with greater infant adiposity.
In an interview with EndocrineWeb, Dr. Hernandez said that until now, most research involving women with gestational diabetes focused on maternal blood glucose. “That has been the only clinical metric we have, but our data implies that we can have an impact on these patients’ insulin resistance even in the third trimester.”
Dr. Hernandez stressed the implications for infant health. “The results demonstrate that higher fat intake makes maternal insulin resistance worse. When there is more insulin resistance, more fuels get across to the infants [while in the womb], which produces fatter babies,” she said. “Our results show that even in a mother who is clinically insulin resistant [by virtue of having gestational diabetes], we can make a difference with diet. We can intervene before birth.”
Dr. Hernandez acknowledged that the HC/LF diet carried an unusually high ratio of carbohydrates at 60%, compared with the conventional dietary recommendation of 55% for people with diabetes. “We’re not advocating a 60% carbohydrate diet, but we needed to ensure that the two diets in the study were different enough to demonstrate their effects in a controlled environment.”
Overall, the results may help to alleviate some fear in pregnant women with gestational diabetes, Dr. Hernandez said. “Many of them are afraid to eat any carbohydrates. They think they can’t have toast or pasta. Our study suggests that they don’t need to be so afraid.”