Hormone Raises Desire for Fattening Foods
TUESDAY June 22, 2010 -- You're dieting, and you know you should stay away from high-calorie snacks. Yet, your eyes keep straying toward that box of chocolates, and you wish there was a pill to restrain your impulse to inhale them.
Such a pill might one day be a real possibility, according to findings presented Tuesday at the Endocrine Society's annual meeting in San Diego. It would block the activity of ghrelin, the "hunger hormone" that stimulates the appetite centers of the brain.
The study, reported by Dr. Tony Goldstone, a consultant endocrinologist at the British Medical Research Council Clinical Sciences Center at Imperial College London, showed that ghrelin does raise the desire for high-calorie foods in humans.
"It's been known from animal and human work that ghrelin makes people hungrier," Goldstone said. "There has been a suspicion from animal work that it can also stimulate the rewards pathways of the brain and may be involved in the response to more rewarding foods, but we didn't have evidence of that in people."
The study that provided such evidence had 18 healthy adults look at pictures of different foods on three mornings, once after skipping breakfast and twice about 90 minutes after having breakfast. On one of the breakfast-eating mornings, all the participants got injections -- some of salt water, some of ghrelin. Then they looked at pictures of high-calorie foods such as chocolate, cake and pizza, and low-calorie foods such as salads and vegetables.
The participants used a keyboard to rate the appeal of those pictures. Low-calorie foods were rated about the same, no matter what was in the injections. But the high-calorie foods, especially sweets, rated higher in those who got ghrelin.
"It seems to alter the desire for high-calorie foods more than low-calorie foods," Goldstone said of ghrelin.
That effect was especially pronounced when the participants fasted overnight before the study was done. "We know that when you fast, you tend to crave high-calorie foods more," Goldstone said. "We mimicked that effect."
So a pill that blocked ghrelin's activity could be useful for dieters, and several drug companies already are working to develop one, he said. It wouldn't be something you could pop when a tempting dish appeared, because the blocking effect would take some time to happen, but it could be part of an overall weight-loss regimen, Goldstone said.
"If developed, it might have the particular effect of blocking the desire for high-calorie foods," he said.
The study results come as no surprise, said Alain Dagher, an associate professor of neurology at McGill University in Montreal, who has been studying ghrelin.
In his research, MRI scans of animals found that "ghrelin increases the brain response to food," Dagher said. "So, it's not surprising that a single injection in humans supports a shift to high-calorie foods in general."
Dagher is continuing his studies. "We've been trying to get more specific about exactly how ghrelin acts on the brain, which brain regions it affects and how those effects translate to eating," he said.
Ghrelin might not play a role in causing obesity, but it might act to keep people obese by reducing their ability to lose weight, Dagher said.
To learn what ghrelin is and does, visit the University of Edinburgh.
Posted: June 2010
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