Study Explains Why Obese People Gain Back Lost Weight Rapidly

Many people who fight the "bulge battle" know that keeping the weight off is far more difficult than losing weight.

A new study from the University of Adelaide has shown that the stomach's nerve response, which signals fullness to the brain, gets damaged in obese people. This may explain why they often gain back the weight after dieting. Researchers found that this system is so severely damaged in these people that it never gets back to normal even after they have lost weight.

"The stomach's nerve response does not return to normal upon return to a normal diet. This means you would need to eat more food before you felt the same degree of fullness as a healthy individual," says study leader Associate Professor Amanda Page from the University's Nerve-Gut Research Laboratory.

Stephen Kentish, a PhD student from University of Adelaide, looked at the effect of high-fat diet on the gut's ability to tell the brain that it is time to stop eating. He also investigated whether the signalling improved after the high-fat diet was changed with a low-fat diet.

Results of the laboratory studies showed that the nerves in the guts didn't tell the brain that the stomach was full even after a switch to a healthy diet.

"A hormone in the body, leptin, known to regulate food intake, can also change the sensitivity of the nerves in the stomach that signal fullness. In normal conditions, leptin acts to stop food intake. However, in the stomach in high-fat diet induced obesity, leptin further desensitises the nerves that detect fullness. These two mechanisms combined mean that obese people need to eat more to feel full, which in turn continues their cycle of obesity." Page said in a news release.

More research is needed to find how the mechanism works and if there is any way that can trick the stomach into resetting itself back to normal, researchers said.

The study is published in the journal International Journal of Obesity.

A diet high in fat makes people addicted to high-fat food resulting in depression and even changes the brain's circuitry a study published in International Journal of Obesity had previously reported.

Obesity can raise risk of chronic conditions such as heart disease, diabetes, stroke, arthritis and even some cancers. According to estimates by Centers for Disease Control and Prevention, a third of all people living in the U.S are obese.