New research out of the Yale-Griffin Prevention Research Center shows why walnuts should play a prominent role in our diets.

The study demonstrated that a diet rich in walnuts helped subjects with obesity shrink their waistlines and improve blood flow. The finding has implications for understanding weight control and reducing the risk for cardiovascular disease, said Director of the Prevention Research Center and the study’s lead author David Katz. The finding was published online in the Journal of the American College of Nutrition on July 25.

“This study shows that in practical terms, incorporating walnuts into the diet corresponds with some improvement of risk factors for heart disease,” said Loma Linda University professor of nutrition Joan Sabaté, who was not involved with the study.

The researchers recruited 46 obese participants with risk factors for cardiovascular disease and Type 2 diabetes. The subjects were divided into two groups, and during the study, all subjects ate normally while one group received an additional 56 g of walnuts per day for eight weeks. After a four-week washout period where neither group ate additional walnuts, the initial control group started on the walnut-enriched diet.

Throughout the study, researchers measured the elasticity of the right brachial artery in order to assess walnut’s effect on blood flow. Results showed walnuts slightly reduced blood pressure and vastly improved blood flow.

Katz said one of the most intriguing results of the study were walnut’s impact on waist circumference. While the presence of walnuts added about 350 calories per day to the subjects’ diets, subjects’ waist circumferences went down instead of increasing, though subjects did not actually lose weight.

“What we think is going on here is that walnuts — nuts in general — but walnuts [in particular are] very satiating so they actually help bump other calories out of the diet,” Katz said. “So if you add walnuts, the benefit isn’t just what you’re adding but also what you’re bumping out.”

Given the results of this study, incorporating walnuts into the American diet may help treat the obesity epidemic by reducing dependency on foods high in saturated fats, said study co-author and Assistant Director of the Prevention Research Center Valentine Njike in an email to the News on Thursday, adding walnuts have been shown to bring benefits ranging from enhanced brain function to reduced stress. Walnuts also have high amounts of alpha-linolenic acid, an omega-3 acid that has proven to benefit the heart, he said.

While snacking has been implicated in obesity, Katz said encouraging nutritious snacks like walnuts should be a key component in public health initiatives going forward. Sabaté said the public should exercise caution in adopting walnuts as “weight-control pills,” though, since they alone will not cure obesity.

Katz is now leading another study to explore the long-term effects of walnut consumption on weight control and diet.

The obesity rate in the United States is 31.8 percent, according to the Robert Wood Johnson Foundation.