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Study Demonstrates Brain’s Role In Obesity

Posted on: Friday, 17 October 2008, 07:55 CDT

Scientists, hoping to get a better understanding of how the brain influences obesity, used a brain scanner on people eating milkshakes and found that when the brain doesn't sense enough gratification from food, people may overeat to compensate.

A blunted response in brain circuitry relating to pleasure could explain why obese people may get less satisfaction from food, U.S. researchers said on Thursday. They said some people may overeat to make up for the decreased pleasure, particularly if they carry a specific gene variant.

"The more blunted your response to the milkshake taste, the more likely you are to gain weight," said Dr. Eric Stice, a senior scientist at the Oregon Research Institute who led the work.

Scientists have long known that genetics also play a major role in obesity - and one big culprit is thought to be dopamine, the brain chemical that's key to sensing pleasure.

Dopamine, a chemical in the brain's reward centers, is released into the body when people eat. The amount of pleasure from food depends on the amount of dopamine released.

The researchers recruited volunteers for the study; 43 female college students, ages 18 to 22 and 33 teenagers, ages 14 to 18. Body mass index calculations showed the young women spanned the range from very skinny to obese.

Brain scans were performed on the participants in order to view blood flow to the dorsal striatum, showing brain activity, as the girls and women drank a chocolate milkshake or a flavorless liquid.

The researchers said the scans showed obese people had less activity in the dorsal striatum, the part of the brain that releases dopamine in response to eating, when they drank a chocolate milkshake, compared to leaner people.

That brain region was far less active in overweight people than in lean people, and in those who carry that A1 gene variant, the researchers said. Moreover, women with that gene version were more likely to gain weight over the coming year.

"The evidence of blunted response leading to future weight gain clearly seems to suggest that people are over-eating in response to this diminished reward that they experience when they eat," said Stice.

He likened it to the way people who smoke regular cigarettes. “If you give them the low-tar cigarettes, they make up for the lost tar by smoking more efficiently, and get more of it," Stice said.

Stice concludes that the study really might show that these people with malfunctioning dopamine in fact eat because they're impulsive.

“If doctors could determine who carries the at-risk gene, children especially could be steered toward recreational sports or other things that give them satisfaction and pleasure and dopamine that aren't food,” said Stice.

Image Courtesy Wikipedia

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On the Net:

• Oregon Research Institute

Source: redOrbit Staff & Wire Reports

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