Obese people anticipate enjoying food more than thin people do. But, according to a new brain imaging study, they actually enjoy it less.
For a long time there's been emerging research showing that there's a brain chemistry component to overeating. Studies by Gene-Jack Wang and others have demonstrated for example that obese subjects have fewer dopamine D2 receptors, meaning they are less "sensitive" to reward, a finding that is similar to what's found in drug addicts. It's as if the pleasure circuits of the brain are "hijacked".
"This makes sense because eating, like other activities regulated by dopamine reward circuits, is a highly reinforcing behavior. The behavior of overeating in obese subjects shares similarities with the compulsive use of drugs in addicted subjects", says Dr. Wang.
Dopamine is clearly involved in eating behavior, even for people who aren't obese. Smelling, seeing, and talking about food -- even without the pleasure of eating it -- increases brain dopamine in non-obese, food-deprived subjects. "This provides evidence of an involvement of dopamine in the motivational behaviors that drive food intake, independent of the pleasure of eating the food" says Dr. Wang.
The new research by Eric Stice, PhD, of the Oregon Research Institute shows that obese people anticipate enjoying food more than lean people do- but when they actually eat it, they enjoy it less.
The researchers showed women subjects two pictures- one of a chocolate milkshake, one of a glass of water. The heavier the woman, the more active the "pleasure circuit" in the brain.
But get this- once the women actually tasted the chocolate milkshake, the heavier ones showed less activity in their brains' pleasure centers than the leaner ones.
Food is one of the many stimuli in our lives that release dopamine, a neurotransmitter associated with pleasure-specifically, the anticipation of pleasure. Think about the time you went on a first date with someone you had a crush on- that rush of pleasure and excitement and anticipation was coming from (you guessed it)... dopamine!
One addiction researcher has wisely called dopamine the "gotta have it!" neurotransmitter, while serotonin is the "Ah! Relax! Got it!" neurotransmitter.
Some people have a variant gene that dulls dopamine responses-these folks are more at risk for being obese (and possibly more at risk for addictions in general). Even if they're not obese, they seem to get less pleasure from eating - which puts them at greater risk of compensating by eating more, possibly in an unconscious attempt to increase dopamine and produce pleasure.
So is the take-home point here that obesity and overeating are "genetic"? No. But it does mean that there are powerful brain circuits involved in reward that can make you more at risk for overeating.
You don't need "genetic testing" on this one. Some proactive, empowering actions can help you combat even a genetic propensity to overeat. Find pleasure in as many things as possible, "spread it around" so that you have a repertoire of pleasurable activities (hopefully non-destructive ones!) and take care of your emotional and spiritual needs as much as possible.
And take a stand for your health. Your genes are not destiny.
Remember, genetics loads the gun. But environment pulls the trigger.