Credit: Wikimedia Commons, Rustedstrings (Roman Oleinik)

Although walnuts are recommended as an effective way to control appetite in people with diabetes, just how they regulate appetite has only recently been discovered. In a new study published in the journal Diabetes, Obesity and Metabolism, researchers examined the brains of 10 obese volunteers who drank breakfast smoothies for five days. Some of the volunteers drank smoothies containing walnuts, while others drank nut-free smoothies that looked and tasted identical. One month later, the participants repeated the study, but this time those who received walnut smoothies during the first trial drank the nut-free beverage and vice versa. Neither the volunteers nor the researchers knew which smoothie the participants consumed during each phase of the study.

At the end of each five-day trial, the volunteers—on an empty stomach—looked at images of “desirable” high-fat foods such as cake and onion rings, healthy foods like fruits and vegetables, and non-edible things like rocks or trees. The people who consumed the walnut smoothies consistently showed more activity in the area of the brain associated with regulating the behavior of eating and feeling satisfied (satiety) when they looked at the high-fat foods. By stimulating this area of the brain called the insula, the researchers think that walnuts promote weight loss by reducing cravings. In fact, the study participants reported feeling less hunger and feeling like they could eat less food after their walnut trial as compared to their nut-free trial.

In addition to reducing food cravings, walnuts are low in saturated fats and high in omega-3 fatty acids and are good sources of fiber and protein. The next time you have the urge to snack, grab a handful of walnuts.

Karen Sweazea, PhD, is an associate professor in the School of Nutrition & Health Promotion and the School of Life Sciences at Arizona State University.