A low-glycemic diet did not result in improvements in insulin sensitivity, lipid levels, or systolic blood pressure, according to research published in the December 17, 2014, issue of JAMA.

Investigators conducted a randomized controlled trial in which 163 overweight adults with elevated blood pressure were given one of four complete diets that contained all of their meals, snacks, and beverages for five weeks. Each diet was a variation of a healthful dietary pattern as recommended by our national dietary guidelines, such as the DASH and Mediterranean diets.

The researchers measured five outcomes, including insulin sensitivity, levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, and systolic blood pressure. In addition, the effects of glycemic index when total carbohydrate is high, as in the DASH diet, or low, such as the OmniHeart diet or Mediterranean diet, were observed.

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“We studied diets that had a large contrast in glycemic index, while at the same time we controlled intake of total carbohydrates and other key nutrients, as well as maintained baseline body weight,” said Frank M. Sacks, MD, a physician and researcher at Brigham and Women’s Hospital, Channing Division of Network Medicine, in Boston.

“We found that composing a healthful diet with low-glycemic index carbohydrate-containing foods rather than high-glycemic index foods did not improve insulin sensitivity, HDL or LDL cholesterol levels, or systolic blood pressure.”