People who have a hard time maintaining weight loss may be able to blame the nerves in their stomach, according to a new study in the 'International Journal of Obesity.'
In the study, researchers put mice on a 24-week high-fat, low-fat, or half and half diet. Then the researchers tested the responsiveness of nerves in the mice's stomachs that act as stretch receptors, signaling fullness to the brain. They found that the nerves of both the high-fat and mixed diet mice were desensitized. In other words, they didn't send "I'm full" signals when they should have, even when the mice returned to healthy eating. "There's not even a sign of it going back," says study author Amanda Page, an associate professor at the University of Adelaide.
Humans have these same nerves in our stomachs. If humans experience the same desensitization, it explains why – in strong, physical terms – formerly obese individuals have such a hard time feeling satiated, even after they've reached a healthy weight.
Don't expect a nerve-calming pill to come out any time soon, though. Beyond these results, this process is a bit of a mystery to scientists. For one, they aren't sure if the desensitization is at all reversible. Researchers also have no idea how long it takes to develop or what exactly causes it. It may be fat in the diet or something about the obese state itself. Page still holds out hope for being able to reverse the process: "Nerves are quite resilient and they are capable of regenerating and resensitizing," says Page. "It's just that these nerves seem to be particularly resistant."