LONDON--A natural hormone that curbs appetite and limits the amount of food people eat could help to stem a worldwide obesity epidemic, scientists said on Wednesday.
More than a billion people are overweight or obese, creating a pressing public health problem because excessive weight is linked to an increased risk of diabetes, heart disease, strokes and certain cancers.
But scientists from Britain, the United States and Canada have discovered that a hormone in the body called PYY3-36 that tells the brain when the body is full could form the basis of new weight-loss treatments.
"The discovery that PYY3-36 suppresses appetite could be of huge benefit to those struggling with weight problems," said Professor Stephen Bloom, of Imperial College London.
"It does cause an inhibition of appetite and reduces food quite significantly," he added in an interview.
Bloom believes it may be possible to identify foods which cause the release of more PYY3-36 so appetite could be limited naturally. Another option would be injections of the hormone, similar to the way diabetics take insulin, which could provide a safe long-term treatment for obesity.
EATING LESS WITHOUT FEELING DEPRIVED
PYY3-36 is released by the gut after every meal. It sends signals to the feeding circuits in the brain that convey a sense of satiety that reduces the urge to eat.
When the scientists compared the effects of PYY3-36 to a placebo on 12 normal-weight volunteers the people who had been given an infusion of the hormone ate 33 percent less over the next 24 hours than the placebo group.
"This is a naturally occurring hormone that affects centres in your brain. It stops you eating because it makes you feel less hungry. It is part of your natural physiology," said Dr Caroline Small, a member of the research team which published its findings in the science journal Nature.
The doses given to the volunteers mimicked the levels that occur naturally in the body after a meal and produced no side effects. People just felt less hungry.
Roger Cone, of Oregon Health and Science University in Portland who contributed to the research, described it as another piece in the puzzle that adds to the understanding of how hunger and satiety are controlled.
But he added that there is still a way to go before PYY3-36 can used to fight the worldwide obesity problem.
Obesity is based on body mass index (BMI), which is calculated by dividing weight in kilograms by height in metres squared. A BMI of more than 30 is considered obese.
Before the hormone can be developed into an anti-obesity treatment, scientists must first show that it produces the same satiety feeling and reduces appetite in obese people. Researchers must also work out better ways of delivering it into the body and determine how it is broken down.
The volunteers in the study received intravenous infusions of PYY3-36 but the researchers think an injection could be produced.
Small said the scientists are conducting further studies and comparing the effects of the hormone infusions on normal-weight and obese people.
"There is a huge epidemic of obesity and treatments are very much needed," she said.
"You need to reduce the amount of food people eat or increase the amount of energy they expend. This would reduce the amount of food people consume by making them satiated. It is enhancing those natural signals in the brain."
LONDON -- Scientists have isolated a hormone that makes people feel full when they eat, and demonstrated its potential as a new weight-loss drug by injecting volunteers with the substance before a big buffet lunch.
The participants injected with the "third-helping hormone" ate one-third less than usual and resisted snacking for as many as 12 hours, scientists reported in Thursday's Nature journal. The hormone infusion was "sort of a fake meal," said the study's senior author, Steven Bloom. "The brain was fooled into thinking that it had already eaten."
The experiment offers a preliminary but promising opportunity to develop a new drug to curb obesity, scientists said. Still, some cautioned that treating overweight people with direct hormone injections may be dangerous.
Researchers in England and Oregon isolated the hormone PPY3-36 that is secreted by cells lining the intestines. Using mice, researchers first identified its effect on the hypothalamus, a part of the brain that regulates appetite. Then, 12 people of normal weight -- six men and six women in their 20s -- were injected with extra hormone or a placebo saline solution. Two hours later, they were offered an Indian-curry buffet lunch -- chicken or vegetarian, spicy or mild.
The volunteers who received the hormone boost ate one-third less than they had at previous meals.
Scientists said the one-time experiment alone doesn't prove the injections can safely control appetite or reverse obesity. How the body may respond to elevated PPY3-36 levels is unclear. More studies are needed, they said.
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