A recent study published in the May issue of Cell Metabolism discovered that a hormone secreted in the gut drives individuals to eat by making food seem more appealing. The hormone, ghrelin, was infused into healthy volunteers who were subsequently shown pictures of various foods while being subjected to an MRI to study the brain’s reward centers. The hormone was found to stimulate not only visual processing of food images but also memory. Volunteers in the study recalled the food images as being particularly appealing even some time after testing. According to Dr. Alain Dagher, M.D., of McGill University, “Ghrelin has widespread effects, not just on one or two brain regions, but the whole network. …After ghrelin infusion food pictures become even more salient — people actually see them better. It influences not only visual processing, but also memory. People remembered the food pictures better when ghrelin was high.” The following is an excerpt of an article from Medpage Today that reviews the study:
To learn more about the origin of ghrelin’s effects on eating, Dr. Dagher and colleagues studied 20 nonobese healthy volunteers.
Three hours after eating a standardized meal, the participants viewed a series of pictures of food and scenery and subjectively rated their appetite and mood. Investigators also examined the participants’ recall of the pictures.
Then 12 participants received ghrelin by intravenous infusion and eight received a placebo infusion.
All participants underwent functional brain MRI and then viewed the same pictures again.
Participants in the ghrelin group demonstrated a significant increase in hunger assessment and recall of food pictures after receiving the hormone (P=0.01) but hedonic ratings did not differ between the two viewings of the pictures.
In the placebo group, neither picture recall nor subjective responses differed between the two viewings.
Brain imaging after administration of ghrelin, versus placebo, revealed heightened neural response in the amygdala, orbitofrontal cortex, anterior insula, and striatum.
“These regions encode the salience and the hedonic and incentive value of visual cues,” the authors said. “This effect likely accounts for the ability of ghrelin to trigger and promote feeding.”