It would be nice to blame that chubby belly on genes rather than
greed. And indeed, a new study suggests that a gene mutation can
cause people to overeat. But things are never that simple. The
same study shows that people with the standard gene can also put
on weight if their brains get a bigger hit from snacking. The
common mutation, in a gene called DRD2 that senses a pleasure-
providing brain chemical called dopamine, causes people to get
less of a high from food - and then compensate by eating more.
"Eating the same éclair is going to be less rewarding to obese
people than to lean people," says Eric Stice, a clinical
psychologist at Oregon Research Institute in Eugene who led the
study. His team scanned the brains of 43 female university
students and 33 teenage girls as they sipped a chocolate
milkshake or a tasteless substitute while in a functional-MRI
machine. In all the participants, the milkshake lit up an area
of the brain called the striatum that senses rewards, whether
food, drugs or money. Women a