The holiday season is tough for anyone to see their weight. Food scenes and scents hard to resist. One of these hunger response factors is the hormones that are found in the stomach, which make us more vulnerable to tasty food flavors, promoting overeating and obesity.
New research on hormone ghrelin was published today Cell Reports 4 December 2018, led by Dr Alain Dagher Laboratory at the Montreal Neurology Institute and McGill University Hospital.
A previous study by Dr. Daghera and others showed that ghrelin promotes the absorption and production of dopamine, a neurotransmitter that is important for rewards. In the current study, researchers injected 38 subjects with ghrelin and exposed them to various flavors for both food and non-food products, while displaying neutral images of random objects, which over time subjects attached images of perfume.
Using functional magnetic resonance imaging (fMRI), researchers recorded activity in the brain regions known to be involved in the dopamine-producing response. They found that activity in these regions was higher for people injected with ghrelin, but only when responding to pictures of the food flavor. This means that ghrelin controls the extent to which the brain attaches rewards to food flavors.
The subjects also appreciated the likelihood of the food-related images, and the results showed that ghrelin both reduced the response time and increased the apparent likelihood of food-related images, but did not affect their response to non-food flavor images.
People struggling with obesity often have an unusual response to a diet that is abundant in our environment, such as a fast-food ad. This study shows that ghrelin may be a major contributor to their elevated dietary response. The identified brain regions are associated with nerve endophenotypes, which cause obesity, which suggests that genetically based hypersensitivity to food-related images and odors.
"Obesity is becoming more widespread throughout the world, and it is well-known that it causes health problems like heart disease and diabetes," says Dr. Dagher. "This study describes the mechanism by which ghrelin makes people more vulnerable to starvation stimuli, and the more we know it, the easier it will be to develop therapies that prevent this effect."
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