September 16, 2013
High Fat Diets Set the Stage For Long Term Obesity
Michael Harper for redOrbit.com - Your Universe Online
It’s commonly understood that those who lose a significant amount of weight have difficulty keeping the weight off and often become trapped in a loop of what’s called “yo-yo dieting.” This struggle highlights the mental transformation which must accompany weight loss in any amount.
New research from the University of Adelaide in Australia, however, notes that people who become obese are even less likely to keep the weight off due to a damaged switch in the stomach that tells the brain it’s full. In other words, even though an obese person loses weight and begins eating less, their brains never register that their stomachs are full and satiated.
This research highlights two key components about obesity: As noted in prior research, obesity can be a vicious cycle of hunger and health risks. Second even after a person loses weight, this faulty switch will continue to urge a person to eat more and return to 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,” explains study leader Amanda Page, associate professor and the university’s Nerve Gut Research Laboratory.
According to Page, the hormone leptin is responsible for desensitizing the nerves in the stomach which relay information to the brain. After being subjected to high-fat diets for long periods of time, this hormone essentially wears away at the stomach nerves and stops regulating food intake. In a healthy person’s stomach, leptin works to let the brain know the stomach has received enough food. This change, says Page, occurs once high-fat diets are introduced and isn’t reversed once a person changes their diet and loses weight.
“Unfortunately, our results show that the nerves in the stomach remain desensitized to fullness after weight loss has been achieved,” said Page. “We know that only about 5% 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.”
It’s not yet known if this effect is long-lasting or if the leptin eventually returns to its normal function.
“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.”
Page isn’t the first researcher to point to leptin as a key player in obesity. Scientists from the Weizmann Institute of Science in Israel found leptin was responsible for regulating appetite and increasing physical activity. Obese people often have an excess of this hormone, but their cells become resistant to it.
The Israeli study looked at the effects of leptin on the body mass of female and male rats.
More than a year later, research from John Hopkins University discovered rats that ate a high-fat diet as babies were more likely to become obese when they grew up. This study also looked at a high fat diet’s ability to reduce the body’s sensitivity to leptin and therefore start a chain reaction which results in the body craving more food even when it’s not hungry.
The results of this study are published in the International Journal of Obesity.