Obesity could permanently destroy appropriate hunger cues - even after weight loss

Your stomach is a smart organ.

It can expand after a large meal, allowing your gastrointestinal tract to handle the extra load. And now, it can even be surgically "shrunk" to assist with weight loss - all while continuing to do its job as normal.

But for people who are already obese, normal hunger cues that alert the body when it need sustenance may be permanently altered, even after a person loses weight. Researchers from the University of Adelaide believe this might be why most people who lose weight on a diet eventually gain it back.

Fullness signals

PhD student Stephen Kentish investigated the stomach's ability to signal fullness in people who consistently ate a high-fat diet. His findings showed that certain nerves in the stomach that alert the brain of fullness are desensitized in obese individuals.

"The stomach's nerve response does not return to normal upon return to a normal diet," study leader Amanda Page said in a press release. "This means you would need to eat more food before you felt the same degree of fullness as a healthy individual."

Leptin, a hormone that normally regulates hunger and food intake, also changes the sensitivity of the nerves, Page said, which further damages the stomach's ability to send proper signals when it's full.

"These two mechanisms combined mean that obese people need to eat more to feel full, which in turn continues their cycle of obesity," she said.

A permanent problem?

Page and colleagues aren't entirely sure if the effect is permanent or just long-lasting, but the team team said the results have "very strong implications" for people who are obese, those trying to lose weight or individuals who want to maintain weight loss.

"Unfortunately, our results show that the nerves in the stomach remain desensitized to fullness after weight loss has been achieved," Page said.

And since only about 5 percent of people on diets are able to maintain weight loss, she concluded, further studies on how long nerve desensitization remains would be helpful.

"More research is needed to determine how long the effect lasts, and whether there is any way - chemical or otherwise - to trick the stomach into resetting itself to normal."

The study is published in the International Journal of Obesity.

Source: University of Adelaide