In the past few years, eating walnuts has been associated with feelings of fullness. A recent study conducted by professors at the Harvard-affiliated Beth Israel Deaconess Medical Center (BIDMC) found what's actually happening in the brain to achieve this.
Led by Drs. Olivia M. Farr and Christos Mantzoros, the scientists used the help of 10 volunteers to live at the Clinical Research Center for two five-day sessions. By having them live there during these sessions, the professors could precisely analyze their nutrition.
During one of the sessions, the volunteers consumed smoothies containing 48 grams of walnuts each day (the daily dose, recommended by ADA). And during the other session, they were given placebo smoothies, nutritionally comparable to the smoothies from the first test which also tasted the same, but containing no walnuts.
As has been the case in other studies, the volunteers reported feeling less hungry during the week that they consumed the Walnuts smoothies. Taking things a step further, each person was placed in an Functional magnetic resonance imaging machine on the fifth day of the session, to have their brains scanned. In that machine, they were shown images, including shots of neutral objects, photos of foods such as hamburgers and desserts, along with pictures of less desirable but healthier foods. When the volunteers who had been drinking the walnut smoothies saw the desirable food pictures, increased activity was detected in an area of their brains known as right insula. This region is associated with the regulation of hunger and cravings.