The answer to controlling your appetite actually grows on trees.
According to a brain imaging study — the first of its kind — conducted by medical researchers at Beth Israel Deaconess Medical Center (BIDMC), eating walnuts activates an area in the brain associated with regulating hunger and cravings.
In order to witness exactly how this member of the tree nut family affects appetite on a biological level, the investigative team recruited 10 volunteers with obesity for two 5-day sessions. During one of the sessions, the participants were instructed to consume daily smoothies containing 48 grams of walnuts, which is the serving recommended by the American Diabetes Association dietary guidelines. In another session, the same adults were asked to indulge in a walnut-free smoothie that not only tasted similar to the walnut version, but was also nutritionally comparable. Neither the volunteers nor the researchers were aware when the real nut smoothie was sipped.
The participants reported feeling less hungry during the week they were given the real nut beverage. When they were tested using a functional magnetic resonance imaging (fMRI) machine, they were shown images of common comfort foods (such as hamburgers and dessert), foods that are considered “less desirable” (like vegetables), as well as neutral, non-eatable objects (like flowers and rocks).
As the pictures of the mouth-watering foods appeared, the fMRI imaging revealed increased activity in a small region of the brain — the right insula — only after the volunteers had enjoyed the walnut smoothie. The study authors explain this area is likely involved in cognitive control and salience, meaning that participants were paying more attention to food choices and selecting the less desirable (aka the healthier options) over the highly desirable (less healthy) options.
“This is a powerful measure,” stated lead researcher Christos Mantzoros, MD, director of the Human Nutrition Unit at BIDMC and professor of medicine at Harvard Medical School in a press release. “We know there’s no ambiguity in terms of study results. When participants eat walnuts, this part of their brain lights up, and we know that’s connected with what they are telling us about feeling less hungry or more full.”
Katherine Brooking, registered dietitian and co-founder of Appetite for Health, tells Yahoo Beauty: “I am not at all surprised about the results since previous research has shown that nuts, including walnuts, can aid in feeling full for longer and managing weight. However, what is interesting is the design of this study and how it showed what areas of the brain are impacted and how walnuts play a role in helping quelling appetite.”
Julie Upton, registered dietitian and the other founder of Appetite for Health, tells Yahoo Beauty that several studies indicate that foods rich in protein and/or fiber offer more satiety. “Nuts, in general, provide both protein and fiber, so that’s a winning combination,” she says. Upton adds that this also explains why other research has found that “nut eaters are thinner than those who rarely eat nuts.”
For those who suffer from a nut allergy, a few other satisfying high-in-protein foods include eggs, Greek yogurt, poultry, and seafood. “The key is to eat protein-rich foods that are low in unhealthful saturated fat, along with preparing them without added fat, i.e. not fried,” says Upton.
As for the best filling high-fiber foods, she suggests opting for beans, fruits, veggies, and whole grains. “These foods are also relatively low in calories; therefore, you can eat a lot of them without filling out,” Upton says. “There is overwhelming evidence that people who eat a more plant-based diet have smaller waistlines compared to those who consume diets rich in meat and dairy foods. [They also tend to have] better appetite control and fewer cravings.”
The authors of this latest study are hopeful that further research could led to new treatments for obesity.
“We plan to use it to understand why people respond differently to food in the environment and, ultimately, to develop new medications to make it easier for people to keep their weight down,” concluded Mantzoros.
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