Overeating leads to brain changes that feed your appetite, researchers find

The Centers for Disease Control estimates a third of American adults are obese, and another third are considered overweight. Now, a new study from the University of Washington may shed some light on why it's so hard to lose weight.

You don't even notice, but the more you eat, the harder it is to feel full. Scientists wanted to find out why.

"The number of people losing weight or stating that they have tried to lose weight over the past year is 50%," said Ellen Schur, MD at UW Medicine Diabetes Institute.

Schur helps patients lose weight. She says weight loss itself causes hormone changes that make food more appealing, so it's harder to keep weight off.

Researchers from UW Medicine Center for the Neurobiology of Addiction, Pain and Emotion found that the body adapts to excess eating.

Mark Rossi and Marcus Basiri's study shows that overeating changes brain cells that suppress food intake.

"We don't know the exact mechanisms that are contributing to it, but we see that there are profound changes across lots of different cell types," Rossi said.

There are many reasons why people overeat. There's stress eating, emotional eating and just eating because you're bored. Previous research found that the combination of salt, sugar and fat found in fast and convenience foods also stimulates overeating.

"So these glutamate neurons, which normally function to suppress feeding, were kind of toning down their firing patterns," Basiri said.

In the study, as the mice got fatter, neurons got worse at putting the brakes on eating. The team hopes this leads to new ways to treat obesity in people one day.

Now, the research team is working on isolating an even smaller set of cells that are affected by overeating.

They haven't yet discovered whether the neurons can change back to how they worked before obesity.