Most people who diet and lose a large amount of weight eventually gain it back. But why? Researchers at the University of Adelaide may have found the reason. They discovered that during the process of gaining weight and becoming obese, the way the stomach detects and tells the brain how full we are becomes damaged. Unfortunately, it does not return to normal once we lose weight.
Researchers believe this could be a key reason why most people who lose weight on a diet eventually put that weight back on.
The results, published in the International Journal of Obesity, show that the nerves in the stomach that signal fullness to the brain appear to be desensitized after long-term consumption of a high-fat diet.
"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.
"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 desensitizes 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."
Associate Professor Page says the results have "very strong implications for obese people, those trying to lose weight, and those who are trying to maintain their weight loss."
"Unfortunately, our results show that the nerves in the stomach remain desensitized to fullness after weight loss has been achieved," she says.
Associate Professor Page says they're not yet sure whether this effect is permanent or just long-lasting.
"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."
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