Walnuts: appetite control by activating targeted brain regions
New and effective diets are reported daily. In general, nuts have long been known as one of the most valuable foods, they have a positive effect on our metabolism and are very well suited for the prevention of cardiovascular disease. Scientists have now demonstrated in a study that especially walnuts are ideal for promoting weight loss during a diet. Walnuts trigger a positive feeling of satiety, which is very beneficial for weight loss.
For the first time, researchers at the Beth Israel Deaconess Medical Center (BIDMC) have demonstrated the neurocognitive effects of walnut consumption in their current research. They discovered that consuming walnuts activates an area of the brain that is responsible for controlling hunger and uncontrollable appetite. The researchers published their findings in the journal "Diabetes, Obesity and Metabolism".
Brain activity in walnut consumption studied
To determine how walnuts work in the brain, scientists have used the functional magnetic resonance imaging (fMRI) imaging technique. They were able to observe brain activity and determine which areas of the brain are activated when consuming walnuts. Ten obese volunteers were taken to the clinic during two five-day study periods where they received a strictly controlled diet. So the scientists did not have to rely on the data from the subjects about their food consumption, but could understand this precisely.
The test subjects received walnut smoothie or Placcebo drink
During a five-day session, subjects received smoothies with 48 grams of walnuts (recommended by the American Diabetes Association) daily. During a second study period, they received a walnut-free, but nutritionally comparable, placebo smoothie flavored with the walnut smoothie. The order of the two study periods was chosen at random, so that some participants first consumed the walnuts and others the placebo. "Neither the volunteers nor the researchers knew in which session they received the nutty smoothie," the BIDMC explains in a press release about the current study results.
Less hunger after walnut consumption
As in previous observational studies, subjects reported in the current study that they were less hungry during the week they were given the walnut smoothies. In the investigation using functional magnetic resonance tomography on the fifth day of the experiment, a clear reason could be established, according to the scientists. After walnut consumption, the subjects showed a significantly increased activity in the brain region, referred to as insula, when viewing images with tasty, rather unhealthy foods and less tasty, fairly healthy foods.
Activation of the insula
The activated area of the insula is probably involved in cognitive control of the decision to eat certain foods, researchers say. As a result, attendees focused more on food choices and opted for healthier, less tasty options. The researchers emphasize that there is no ambiguity in the study results.
"When participants eat walnuts, that part of their brain shines and we know that this is in line with what the test subjects say: they are less hungry and more comfortable," says research leader Christos Mantzoros.
Influence of food on brain activity
"We don't often think about how our eating habits affect activity in our brain," says study author Olivia M. Farr of the Department of Endocrinology, Diabetes and Metabolism at the BIDMC. The current study clearly shows that there is also evidence in brain activity for well-being and lower hunger after walnut consumption. In other words, ingested food has direct neurocognitive effects in the brain, which in turn have a significant influence on eating behavior.
In a next step, the researchers plan to test different amounts or dosages of walnuts to see if more nuts lead to more brain activation or if a maximum effect is achieved after a certain amount. In addition, the neurocognitive effect of other foods must also be investigated. (Fp)