Stomach damage means diets are doomed to fail, researchers say
The way the stomach detects and tells the brain how full the body is becomes damaged in obese people, but does not return to normal once they lose weight, according to new research from the University of Adelaide.
The results, published in the July 2013 issue of the International Journal of Obesity, showed that the nerves in the stomach that signal fullness to the brain appear to be desensitised after long-term consumption of a high-fat diet. Researchers believe this could be a key reason why most people who lose weight on a diet eventually put that weight back on.
“The stomach’s nerve response does not return to normal upon return to a normal diet,” said Associate Professor Amanda Page from the University of Adelaid’s Nerve-Gut Research Laboratory and the study’s lead author. “This means you would need to eat more food before you felt the same degree of fullness as a healthy individual,” she said.
According to the researchers, a hormone in the body called 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,” Associate Professor Page said. “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,” she said.
Associate Professor Page said the results have “very strong implications for obese people, those trying to lose weight, and those who are trying to maintain their weight loss”.
The researchers said there were not yet sure whether the desensitisation of the stomach nerves is a permanent effect, or just a long-lasting one.
“We know that only about 5 per cent of people on diets are able to maintain their weight loss, and that most people who’ve been on a diet put all of that weight back on within two years,” Associate Professor Page said. “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,” she said.
The study was funded by the National Health and Medical Research Council (NHMRC).