Anti-obesity vaccine: truth or myth?

The target of this vaccine is ghrelin, a recently discovered hormone that decreases energy expenditure and fat breakdown. Scientists at the Scripps Research Institute in California reported in this week's issue of the Proceedings of the National Academy of Sciences that they have developed a way to make the immune system produce antibodies that attack ghrelin, and that rats given the vaccine ate normally but lost weight, HealthDay News reports.

The immune system thus produced antibodies that bound to and deactivated ghrelin, just as vaccines against diseases caused by bacteria or viruses bind to and inactivate them, according to Forbes.

Researchers vaccinated 17 rats, tricking their bodies into rendering a protein linked to weight gain ineffective and causing the rats to put on less weight than untreated animals. Humans have the same protein, according to the study published yesterday in the Proceedings of the National Academy of Sciences.

In the study, three groups of rats each were repeatedly given different vaccines against the protein, called ghrelin. They ate normally, and once the vaccination started working, they gained less weight and less body fat than animals which hadn't been immunized. This means their bodies had become less effective at metabolizing food.

The animals whose blood showed the vaccine working most effectively gained the least amount of weight, about 0.8 grams a day, compared to a weight gain of around 1.6 grams for the control group.

Ghrelin, which was only discovered seven years ago, is thought to be the body's evolutionary response to fluctuating food supplies, making those genetically predisposed to store fat more likely to survive, Bloomberg reports.

Over the years, demand by doctors has been high for even moderately effective diet drugs because obesity is so closely tied to diabetes, heart disease, stroke, cancer and arthritis. An adult male 20 percent over the maximum desirable weight for his height is considered obese, U.S. guidelines say.