In an analysis of dietary patterns of postmenopausal women using data from the Women’s Health Initiative Observational Study, researchers at the USDA/ARS Children’s Nutrition Research Center at Baylor College of Medicine and Texas Children’s Hospital found that those who consumed the fewest carbohydrates had a significantly reduced risk of gaining 10 percent of their body weight over an eight–year period, whereas those who consumed the least fat had a significantly increased risk of gaining more than 10 percent of their body weight over that time period.

Their report appeared in the British Journal of Nutrition.

Researchers analyzed four dietary patterns that are common in the general population to see which was predictive of a 10 percent weight gain over eight years: a diet that was low in fat compared to the rest of the population, a diet relatively low in carbohydrates, a Mediterranean–style diet and a diet that adhered to the Dietary Guidelines for Americans that is released by the U.S. Department of Agriculture and updated every five years.

Researchers used data from more than 93,000 women who were a part of the Women’s Health Initiative Observational Study. Their habitual diet was measured at baseline and at year three, and they self–reported their height and weight over the eight–year period. Researchers controlled for caloric intake and physical activity.

“We found that when we adjusted for some potential confounders such as socioeconomic status and age, people who ate the least fat, when we followed up with them eight years later, had a significantly increased risk of gaining more than 10 percent of their body weight, and the same pattern was seen for those following the Dietary Guidelines for Americans,” said Dr. Alexis C. Frazier–Wood, assistant professor of pediatrics at Baylor and the CNRC and senior author of the paper. “We saw no association with following a Mediterranean–style diet and risk of weight gain, and we found that those who ate the least carbohydrates had a significantly reduced risk of gaining 10 percent of their weight over an eight–year period.”

Frazier–Wood and the first author Dr. Christopher Ford did not look at other risk factors or outcomes such as cardiovascular disease or diabetes.

“This is a first step – I would not make recommendations for diet changes based on this study alone, but it is suggesting that too many carbohydrates in the diet are not helpful from the point of view of weight gain,” said Wood. “These data are in line with other emerging evidence, which collectively emphasize the need to consider carefully the dogma that reducing fat from the diet is helpful for obesity prevention.”

Frazier–Wood said that the next steps would be determining whether changes to someone’s diet changes their risk of weight gain, looking at why we see such an association and whether it is dependent on the type of carbohydrate or fat eaten, and then looking at other health outcomes, such as whether metabolic rates, glucose sensitivity and insulin sensitivity are different between the various diets.