When you ingest a stomach hormone called ghrelin it causes your brain to respond to food the way junkies respond to drugs. You are filled with an intense desire for it, and eating it becomes far more memorable. Researchers at Montreal's McGill University studied people's reactions to food after they had ingested ghrelin, and discovered that it made them crave whatever food they were shown in pictures — even if they had just eaten. Drugs that tamper with ghrelin are just around the corner.
Since ghrelin isn't regulated, a fast food restaurant that wanted to sell more food could easily turn it into an additive in their hamburgers or donuts, essentially "addicting" people to their food. Or making them hungrier so that they buy more.
On the other hand, drugs that tamper with ghrelin could also be made to have the opposite effect. they could be used in diet pills to make you feel less hungry, and make food less memorable or appealing. Reports New Scientist about such drugs:
But they might have unintended behavioural side effects, as well, [researcher Alain] Dagher says. Meddling with ghrelin levels could alter the brain's natural sense of rewards, potentially causing mood changes and even depression.Ghrelin drugs seem pretty much inevitable, though one wonders what the warnings in tiny print will say on the labels. Perhaps: "Warning: This may change your perception of rewards."
A diet drug called rimonabant that acts on a similar but separate brain system has been linked to depression and suicide, and although it is on sale in other countries, the US Food and Drug Administration has been slow to approve the pill.
But knocking out ghrelin could help scientists pick apart the hormone's effects on the brain, says Matthias Tschop, an obesity expert at the University of Cincinnati.
"Does the pizza not smell that good anymore? Does the pizza not look as good anymore?" he adds.
Research in mice and rats suggests that the hormone changes how they see and smell food, and the same might be true in humans.
Stomach Hormone turns Hungry People into Junkies [New Scientist]