fMRI tests revealed increased activity in right insula, the part of the brain that regulates satiety and cravings, after participants consumed walnuts. Credit: Beth Israel Deaconess Medical CenterAug. 17, 2017 (MedicalXpress) -- Packed with nutrients linked to better health, walnuts are also thought to discourage overeating by promoting feelings of fullness. Now, in a new brain imaging study, researchers at Beth Israel Deaconess Medical Center (BIDMC) have demonstrated that consuming walnuts activates an area in the brain associated with regulating hunger and cravings. The findings, published online in the journal Diabetes, Obesity and Metabolism, reveal for the first time the neurocognitive impact these nuts have on the brain.

"We don't often think about how what we eat impacts the activity in our brain," said the study's first author Olivia M Farr, PhD, an instructor in medicine in the Division of Endocrinology, Diabetes and Metabolism at BIDMC. "We know people report feeling fuller after eating walnuts, but it was pretty surprising to see evidence of activity changing in the brain related to food cues, and by extension what people were eating and how hungry they feel."

To determine exactly how walnuts quell cravings, Farr and colleagues, in a study led by Christos Mantzoros, MD, DSc, PhD hc mult, director of the Human Nutrition Unit at Beth Israel Deaconess Medical Center and professor of medicine at Harvard Medical School, used functional magnetic resonance imaging (fMRI) to observe how consuming walnuts changes activity in the brain.

The scientists recruited 10 volunteers with obesity to live in BIDMC's Clinical Research Center (CRC) for two five-day sessions. The controlled environment of the CRC allowed the researchers to keep tabs on the volunteers' exact nutritional intake, rather than depend on volunteers' often unreliable food records - a drawback to many observational nutrition studies.

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