No nut is going to control me, you may say. You are your own person. You eat what you want when you want. But science may say otherwise about walnuts.
What is up? Five researchers from the Beth Israel Deaconess Medical Center in Boston (Olivia M. Farr Ph.D., Dario Tuccinardi M.D., Jagriti Upadhyay M.D., Sabrina M. Oussaada, and Christos S. Mantzoros M.D., D.Sc., Ph.D.) conducted a study published in Diabetes, Obesity and Metabolism. The researchers first randomly assigned 10 hospitalized patients with obesity five straight days of either a smoothie with 48 grams of walnuts or a similarly tasting and textured smoothie without walnuts. After one month of returning to their original diets, those who first got the walnut smoothie then got five days of the non-walnut smoothie and vice versa. One participant eventually dropped out of the study, leaving nine who completed the whole protocol.
At the beginning of the study, the researchers measured each of the study subjects’ brain activity using a functional magnetic resonance imaging (fMRI) machine. After the five-day smoothie diet, study subjects then underwent another fMRI to see how things had changed.
Then there was the food porn. The researchers showed the study subjects different pictures while undergoing the fMRI. Pictures included those of “highly desirable foods” (high-calorie or high-fat images, e.g., cakes, onion rings), “less desirable foods” (low-calorie or low-fat images, e.g.,, vegetables and fruits) and “non-foods” (e.g., flowers, rocks, trees). Yes, you rock and flower eaters may say that everything’s subjective, but these were the designations by the researchers. Before and after each fMRI scan, study subjects completed visual analog scales (VAS) to measure how hungry or full they felt.
The study resulted in two major findings. First, after the walnut smoothie diet, study subjects reported feeling less hungry than after the non-walnut smoothie diet. Secondly, following the five days of walnut smoothies, study subjects had differences in their brain activity (as measured by fMRI) when shown food porn. Specifically, the right insula part of the brain seemed to be more active. Parts of the insula may be responsible for satiety and inhibition. In other words, something about walnuts may be telling your brain to simmer down when shown mouth-watering food. This could be some Vulcan mind-meld-like stuff: walnuts may help you control your appetite and thus help with managing your weight.
Of course, this is a very small study with measurements taken only over a short period of time. It also does not prove that walnuts can actually control your appetite or if any of the findings will persist over time. Effects can wear off as the brain and body get used to eating a certain type of food. More, larger, and more complex studies are needed before drawing stronger conclusions. But these results are encouraging. Note that the California Walnut Commission (CWC) did provide funding for this study. However, they were not directly involved in designing, conducting, interpreting, or reporting the results for the study.
Cravings may be due to an ongoing conversation among your brain, your body, the food you’ve already eaten, and the cues in front of you.