The holiday season is difficult for anyone who observes their weight. Food sights and smells are hard to withstand. One of the factors in this hungry response is a hormone found in the stomach that makes us more vulnerable to the delicious smell of food, encouraging overeating and obesity.
New studies of hormone ghrelin have been published today Cell Reports on December 4, 2018, led by Dr. Alain Dagger's Laboratory at the Nuremberg Institute in Montreal and a hospital at McGill University.
Previous studies by Dr. Dagger and others have shown that ghrelin promotes the nutrition and production of dopamine, a neurotransmitter that is important for the response to the reward. In the present study, researchers injected 38 grylin subjects and exposed them to a variety of food and non-food smells, showing neutral images of random objects, so that over time the subjects associate images with odors.
Using functional magnetic resonance imaging (fMRI), the researchers record activity in the areas of the brain known to be involved in the dopamine response. They found that activity in these regions was higher in patients injected with ghrelin, but only when they responded to food-related images smelled. This means that ghrelin controls the degree to which the brain connects the reward with food smells.
Subjects also appreciate the pleasant picture of the smell of food, and the results show that ghrelin reduces response time and increases the perceived appetite of food-related images but does not affect their response to non-food smell,
People who struggle with obesity often have abnormal responsiveness to nutritional feats that are abundant in our environment, such as fast-food advertising. This study shows that ghrelin can be a major factor in the increased food response. Established brain regions are associated with a neuronal endophenotype that confers obesity vulnerability, suggesting genetically-based hypersensitivity to food-related images and odors.
"Obesity is becoming increasingly common in the world and is known to cause health problems such as heart disease and diabetes," said Dr. Dagger. "This study describes the mechanism by which ghirn makes people more vulnerable to starvation stimuli, and the more we know about it, the easier it will be to develop therapies that counteract this effect."
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