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Weight-Loss Vaccine Is Big News

August 7, 2006

Scientists have developed a vaccine that targets the hormone ghrelin, a hormone involved with weight gain and regulating metabolism. The result: the rats eat, and don’t get fat.

The finding has encouraging implications for overweight and obese people, particularly because ghrelin is believed to play a role in the weight regain that plagues many dieters after they lose pounds. The study results were reported in The Sydney Morning Herald.

Scientists believe that ghrelin may have offered evolutionary advantages for humans when food-supplies were irregular. By helping to add weight back on when a person has trimmed down, the hormone would ensure that calories consumed during times of famine would be maximally utilized through storage in the body (thus returning the body to its greatest weight).

In modern times, however, this evolutionary advantage works against humans who have a constant supply of food – that is, if the body becomes overweight or obese, it “sets” itself to remain so.

Studying the Vaccine

Researchers based at the Skaggs Institute for Chemical Biology in California used three different vaccines to vaccinate male rats against several types of ghrelin. The rats were allowed to eat as much as they wanted.

Two of the three vaccines prevented weight-gain in the rats. Rats receiving the vaccine ate the same amount as the control group, which did not receive the vaccine. At the end of the study, the rats receiving the vaccine kept a higher level of muscle mass versus fat – a fact that suggests the vaccine directly affected metabolism, as well as appetite.

Moreover, the rats with the strongest immune response to the vaccine had the lowest levels of ghrelin in their brain, according to study leader Dr Kim Janda, who noted this finding suggests that keeping ghrelin out of the central nervous system helps with weight control:

"The results demonstrate a proof of the principle that active immunization against ghrelin can be used to control weight gain and adiposity in mammals," Dr Janda reportedly wrote in Proceedings of the National Academy of Sciences.

Implications for Obesity

Despite its novel effects, the vaccine has sparked some skepticism, among them Professor John Shine, executive director of Sydney’s Garvan Institute of Medical Research. Professor Shine said that, while the study signaled a significant advance, he thought it unlikely that immunizing against one hormone would results in long-term weight loss, according to the Sydney Morning Herald:

"The whole issue of regulation of appetite and obesity is obviously a very complex jigsaw puzzle, involving complex feedback mechanisms," Professor Shine reportedly said. Blocking ghrelin may simply cause other weight-gain chemicals within the body to take its place.

He added that, until ghrelin’s role in the body is well understood, trialing anti-ghrelin vaccines in humans may be dangerous.

At last - all you can eat and never get fat, The Sydney Morning Herald, August 2, 2006.

Posted: August 2006