You're looking at a group of neurons that are responsible for helping you regulate how much you eat. They're called satiety-promoting melanocortin neurons, and when they're doing their job, they help you feel full when you've had enough to eat.
But when these neurons don't fire, your ability to feel satisfied (i.e. sated) when eating basically goes away. But you can't blame your voracious appetite on these brain cells alone — not entirely, at least. Researchers at Yale School of Medicine have now shown that lack of activity in these neurons is the result of a previously unknown response to molecules known as free radicals. The thing is, too many free radicals in your body can give rise to a whole separate set of biological problems.
Here's a basic rundown of how it works. When you eat a meal, levels of free radicals known as reactive oxygen species (ROS) spike in your brain. The issue with free radicals is that, while they'll help you realize that you should probably cool it with the whole I'm-not-hungry-I-just-feel-like-eating shtick, they're also notoriously bad for your body. Yale's Tamas Horvath, senior author of the study, explains:
"It's a catch-22...On one hand, you must have these critical signaling molecules to stop eating. On the other hand, if exposed to them chronically, free radicals damage cells and promote aging."
It so happens that brain cells recognizes this catch-22 when they sense that you've gotten into the habit of eating too much too regularly. Unfortunately for those of us who like to overeat, instead of cutting their losses by forcing you to stop eating, the neurons simply cut back on their generation of free radicals.
On the one hand, this is good news — the way your body sees it, no more free radicals means no more cell damage. On the other hand, it's downright terrible news, because it results in a vicious cycle wherein overeating leads to a decrease in free radicals; a decrease in free radicals keeps your satiety neurons from firing; lazy satiety neurons prevent you from feeling full, which causes you to overeat; and overeating, in turn, leads to a decrease in free radical production...
You see where this is going.
So what's the take home message? If you can help it, try not to start down the path of overeating, because your biology could wind up working against you. Horvath suspects that the Dr. Jekyll & Mr. Hyde role of free radicals in the body may explain, for example, why it has proven difficult to develop therapeutic strategies for obesity without having to deal with serious side effects.
While future studies will certainly explore whether a sense of satiety can be achieved without flooding the brain with an excess of free radicals, the fact of the matter is that for many with malfunctioning satiety neurons, the long term answer to hunger pangs probably lies in being especially mindful of whatever you're consuming, making sure your brain doesn't trick you into eating more than you need to.
Via Nature Medicine