14 October 2009

An obesity vaccine in the making

An article on the development of an "obesity vaccine" made headline news this week. Join DietDoc as she takes a look at the science behind the breakthrough.

An article on an "obesity vaccine", both on and in newspapers, made headline news this week.

Millions of overweight and obese people all over the world must have read the article with renewed hope that one day soon there will be a solution to their weight problem.

The article announced that researchers at the Scripps Research Institute in California had published a report in the Proceedings of the National Academy of Sciences that they are making progress in developing a vaccine that will combat obesity.

The vaccine will purportedly stimulate the immune system to recognise a hormone called ghrelin, and deactivate it. Experiments with rats have shown that the animals who were vaccinated ate normally, but lost up to 30% of their weight.

These rats were, however, also fed a low-fat, low-energy diet. And, at this stage, the scientists aren't sure if the ghrelin vaccine will work when humans follow their usual fat-rich, high-energy diets.

What is ghrelin?
Ghrelin is the name that has been given to a peptide released by the stomach, which stimulates growth hormone release and appetite, as well as deposition of fat in the human body.

A peptide can be compared to a string of amino acids. Ghrelin is classified as a hormone, because it is produced by the human body and stimulates the above-mentioned metabolic processes.

Researchers have found that ghrelin release makes human beings feel hungry, which leads to an increase in food intake, which in turn causes weight gain that may lead to obesity. Control of the amount of ghrelin secreted by the stomach, with the help of this new vaccine, may possibly prove to be a method of preventing weight gain and obesity.

Problems with ghrelin control
Earlier studies with ghrelin showed that levels of this hormone rise sharply before meals and then decrease immediately after eating. In obese subjects, who lost up to 17% of their body weight by dieting for a period of six months, the ghrelin levels rose by 24%.

This may explain why our bodies actively resist weight loss because we produce ghrelin to counteract our attempts to eat less. It has been suggested that we need to 'trick' our bodies into accepting the lower energy intake used in slimming diets, so that we don't produce more ghrelin and start eating more to compensate – a practice that hampers weight loss. At the moment, we can only resort to exercise to accomplish this deception.

However, if this new anti-ghrelin vaccine is perfected, we may be able to use it to stop our bodies from sabotaging attempts at weight loss.

How long will dieters have to wait?
Despite the exciting promise of this newly discovered vaccine, it may still take a long time for it to become available for human use. The Scripps researchers have warned that they are still in the early stages of developing and testing the vaccine.

The process that pharmaceutical companies must abide by when they develop a new drug is finicky, expensive and can be drawn out for years on end. New drugs have to be tested exhaustively, first in animals and then in human volunteers – a process that can take years to complete.

At the moment, Dr Janda, a professor of chemistry at the Scripps Research Institute, said that it may take up to two years before human trials with this new ghrelin vaccine are initiated.

Until such tests with humans are carried out, we won't know if the ghrelin vaccine will work in human beings and if it will actually cause humans to lose weight. We will also have to wait for human trials to show if the ghrelin vaccine has any negative side-effects that would prevent it from being approved for use.

The chances are also good that when the ghrelin vaccine is eventually marketed, it will be very expensive. This should, however, not stop desperate dieters from using what promises to be a 'magic bullet' for weight loss.

People who are burdened with obesity and have tried every diet, slimming aid and treatment in the book without success, will pay anything to achieve the elusive goal of weight loss.

Hope for the future
It has previously been observed that when the stomach is 'excluded' by means of a gastric bypass, very little or no ghrelin is produced by the body, which may be one of the reasons why people lose so much weight after a gastric bypass.

So, if ghrelin production can be stopped by the new vaccine, we can hope that a similar loss in weight will be the result.

What no one knows at present is if the vaccine will stop ghrelin permanently or if people would need to have repeated shots of vaccine to lose weight and keep it off. But no one would mind having a vaccination, say once a year, to guarantee a slim figure and freedom from obesity.

Let's hope that the scientists who are working on the ghrelin vaccine will progress as swiftly as possible and that, in a few years, anyone struggling to lose weight can pop round to their doctor for a vaccination that will cure them of this problem forever. – (Dr Ingrid van Heerden, DietDoc, August 2006)

Read more:
Obesity vaccine on the cards
Obesity shot on the way?


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