Findings: Hormonal help for the obese

May 2, 2003

Research by the group that discovered the gene that tells people they have had enough to eat could lead the way to a more practical treatment for obesity, writes Martin Ince.

Steve Bloom of Imperial College London and his team discovered the PYY-36 hormone, which signals to the brain when enough food has been eaten. It is found in all mammals, including humans, in essentially the same form. In a paper submitted to the New England Journal of Medicine , Professor Bloom says that PYY offers more hope of a successful obesity treatment than other possible treatments such as leptin, a hormone produced from fat.

"Obese people have more leptin than normal in their bloodstream because they are resistant to it," Professor Bloom said. "But even obese people feel full after a meal, because of the effect of PYY."

Professor Bloom said in a lecture at Imperial on Tuesday that PYY would be hard to abuse, for example by anorexics wanting to restrain their food intake.

"If PYY was taken as a pill it would be highly toxic because it has a wide range of effects in the body. To treat obesity in isolation it would have to be injected straight into the bloodstream, as diabetics do with insulin, so it would be hard to misuse. Otherwise, it would not get to the part of the brain you need to affect."

He said that there were at least eight obesity treatments at the stage of human trials. "The problem with all these is that they have far wider effects on the body than you want. For instance, there is one called Axokine that mimics the effects of flu, because people with flu tend not to eat much. This means that you are affecting the whole immune system. By contrast, I think that PYY is a more natural approach because it works the way the body works."

Professor Bloom said: "You have to be sure there are as few side-effects as possible. Some of the proposed treatments involve cannabinoid drugs, which affect a huge range of receptors in the brain. That sort of interaction is very hard to regulate artificially."

He added that in the UK alone there were about 1,000 deaths a week related to obesity. "Obese people commit suicide more often, get paid less, are promoted at work less frequently and have less sex," he said.

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