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Page: << Prev | 1 | 2 | 3 | Next >> Following the first viewing, 12 of the men received two intravenous infusions of ghrelin, while the other eight did not.
Following blood sampling to gauge hormonal levels, the men viewed a second set of 45 different images.
Dagher and his associates found that during the second viewing, reports of hunger were significantly higher among men who received an infusion of ghrelin.
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This increased hunger response correlated with an increase in brain activity in a broad range of brain regions associated with reward -- but only when viewing food imagery. Activated regions included the amygdala, the right hippocampus, the anterior and mid-dorsal insula, and the left pulvinar regions.
By contrast, men who never received ghrelin expressed no change in hunger over the course of the two viewing sessions and were less likely to remember the food imagery they saw following the viewings.
The researchers suggested that the findings could ultimately lead to treatments for obesity based on a disruption of the ghrelin effect.
"The problem today is that we have this evolutionary imperative to eat, but we now live in an environment where you don't have to spend any energy to get food," he noted. "Which means that it makes sense to think of appetite as a kind of addiction. So, if we want to address the fact that obesity is now the number one killer in the world, we're going to have to tackle the problem in the same way that we tackle cigarette smoking."
But Dr. Barbara B. Kahn, chief of the division of endocrinology, diabetes, and metabolism at Beth Israel Deaconess Medical Center in Boston, cautioned that equating ghrelin-fueled overeating with drug addiction may do a public disservice.
"This study provides us with new information about additional ways in which this particular hormone may work," she said. "And overeating and drug addiction may converge on some of the same neurons. But other pathways are also involved. And from a biochemical point of view, the two are not the same thing. Drug addictions are much stronger. So to suggest that they are the same makes people feel that they can't do anything about overeating. That it's out of their control.
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