Walnuts interact with the brain to help appetite control.  While it has long been suspected that walnuts reduce overeating due to their nutrient-packed makeup, a new study administered by Harvard professor Christos Mantzoros at a Boston medical center recently proved that consuming walnuts indeed activates a part of the brain linked to hunger and cravings. Participants were in a lab environment for ten days, which increased validity because experimenters knew exactly what each participant was eating when. During five days of consuming a walnut smoothie each day and five days of consuming a placebo smoothie that tasted the same, participants consistently reported feeling fuller when having consumed walnuts. The fMRI test in which participants were shown desirable foods, neutral objects, and less desirable foods backed this up. As Mantzoros says, “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.”