"Picture a fat slice of chocolate cake, its thick caramel glaze oozing onto a plate. Your brain, right now, is thinking just like a junkie's, a new study suggests.
When volunteers received a dose of a natural hunger-inducing hormone called ghrelin, their brains responded to pictures of food in the same way that addicted people's brains do to cigarettes or drugs, says Alain Dagher, a neurologist at McGill University in Montreal, Canada, who led the study.
This mechanism probably helped humans to load up on life-saving calories when food was scarce - a likely scenario during much of evolutionary history. But with well-stocked supermarkets and a fast-food outlet on every corner, such brain signals can make food addicts of us all.
Stimulant effect
Made in the stomach, ghrelin levels rise when people are hungry and wane after a meal. People who get injections of the hormone gorge themselves, while those suffering from a rare disease that keeps ghrelin levels unusually high tend to be obese overeaters.
"I think it's the most powerful appetite stimulant that has ever been found," Dagher says.
To test the hormone's effect on the brain, his team gave a small dose to 12 people a few hours after breakfast. Then, the researchers scanned the subjects' brains while they looked at pictures of pizza, hamburgers and other tempting foods. Dagher's team compared the results to brain scans taken before volunteers received the dose of ghrelin."
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