How Fat Vaccines Will Work

A close up of a woman getting vaccinated.
Obesity is steady on the rise. d3sign / Getty Images

According to the Centers for Disease Control and Prevention, about a third of Americans are obese. But if Americans are getting heavier, it's not for a lack of trying to stay slim. People in the United States spend an estimated $30 billion each year on diet pills, diet foods, videos, health clubs, and other tools to help them lose weight [ref].

The quest for a quick and easy weight loss fix has kept scientists in laboratories all over the world busy for decades. Recently, a company in Switzerland has announced that it may have a novel solution: a fat vaccine. Unlike vaccines for polio and the flu, which ward off disease, the fat vaccine would treat obesity. But could a vaccine really help people shed pounds?


In this article, we'll look at the "fat vaccine," see how it might work, and find out whether it could be the long sought after solution to an expanding waistline.

How Vaccines Work

The idea of a vaccine is simple: When the immune system is exposed to a weakened or dead version of a virus or bacteria, it produces antibodies to that disease. Antibodies are specialized proteins in the blood that go after and destroy viruses, bacteria, and other foreign substances.

Press play to learn more about how vaccines work.


If the animation above isn't working, click here to get the Shockwave player.

The next time that person is exposed to the same disease, their immune system remembers it and can quickly launch antibodies to fight off the infection. This is called immunity.

In the past, vaccines were used only to prevent disease. Today, researchers are creating vaccines that can actually treat conditions, including obesity. What sets the obesity vaccine apart from other weight-loss drugs is that it enlists the help of the immune system to induce weight loss.


Ghrelin and Immune Response

The "fat vaccine" is under investigation by Cytos, a Swiss biotechnology company. Currently called CYT009-GhrQb, the vaccine's purpose is to create an immune response in the body against ghrelin, a peptide (a short chain of amino acids, the building blocks of proteins) released by cells in the stomach. Scientists don't know exactly how ghrelin works, but several studies have shown that it stimulates appetite. In one study of anorexic patients, people given ghrelin were hungrier and ate more than those given a placebo. Blood levels of ghrelin quickly rise after people lose weight, which may be why so many people have trouble keeping the weight off. Studies have also indicated that bariatric surgery works, in part, because ghrelin levels drop when the stomach has been reduced.

The CYT009-GhrQb vaccine instructs the immune system to release antibodies that attach to ghrelin and hold it in the bloodstream. This keeps the peptide from making its way into the brain and triggering the feeling of hunger.


But will the vaccine actually cause people to lose weight?

Of Mice and Men

Photo courtesy Office of NIH History

Researchers still don't know whether CYT009-GhrQb is safe and effective. In mice, the vaccine was able to produce high levels of antibodies. Mice on a high-fat diet who were vaccinated gained 15 percent less weight than unvaccinated mice.

Whether the vaccine works on humans is still unknown. Cytos Biotechnology has recruited 112 obese participants who will receive six months of treatment with CYT009-GhrQb followed by six months of careful monitoring. Researchers expect to have preliminary results from the study by late 2006.


Even if the vaccine causes the appropriate immune response, it won't simply melt away the pounds, because it only regulates the desire to eat. People who take the vaccine will still have to be conscious about diet and exercise. But with less of an urge to eat, patients may find it easier to eat smaller portions and stick to a low-fat diet. People who take the drug may need repeated injections until they lose a sufficient amount of weight.

Researchers also don't know whether the vaccine will cause side effects -- the Cytos study will help pinpoint the risks. But some doctors say that using the immune system to modify the body's normal appetite signaling system could be risky and lead to other eating problems.


Other New Anti-Obesity Treatments

Photo courtesy Image After

So far, CYT009-GhrQb is the first true "fat vaccine" to enter human clinical trials. But it's not the only treatment designed to combat obesity. Since the Food and Drug Administration removed the diet drug combo called "fen-phen" from the market in 1997 because of potentially deadly heart-valve problems, the agency has approved two obesity drugs, Xenical and Meridia. Both are currently available by prescription (read more about them in How Diet Pills Work). Several other anti-obesity drugs are further back in the research and development pipeline:

Acomplia is sometimes referred to as the "munchies drug," because it acts on the brain in the opposite way of marijuana. Scientists developed the drug after noticing that people who smoked marijuana often experienced food cravings, or "the munchies." These food cravings occur when substances in marijuana called cannabinoids act on cannabinoid receptors in the brain. Scientists figured out that by blocking those receptors, they could control food cravings. In a study of 1,500 obese or overweight people, participants who took 20 milligrams of Acomplia for a year and cut 600 calories out of their diet lost about 14 pounds, compared with only 4 pounds among people who took a placebo. The participants also lowered their cholesterol, triglycerides (fats that circulate in the bloodstream), and insulin resistance (a condition in which the body does not effectively take glucose, or sugar, into the cells). Although Acomplia is not yet available in the United States, its manufacturer, French pharmaceutical company Sanofi-Aventis, is applying for an FDA license to market the drug here by 2006.


British researchers are working on an anti-fat injection containing the hormone oxyntomodulin, which is naturally found in the small intestine and lets the brain know that the body is full. Researchers believe that injections of this hormone could help obese individuals eat less. In one small study, people who took oxyntomodulin lost about 4 Ā½ pounds more than people who took a placebo. Researchers say they will need to conduct more studies to confirm whether this treatment is effective. Although oxyntomodulin is sometimes called a "fat vaccine" in the media, it is not a true vaccine because it does not involve the immune system.

The German-based Noxxon Pharma is working on another drug called Spiegemler that, like the CYT009-GhrQb vaccine, targets ghrelin to battle obesity. But unlike the vaccine, Spiegelmer does not involve the immune system. Instead, it binds to and neutralizes ghrelin in the blood to control appetite. In a seven-day study, mice that were given the drug lost more weight than a control group.

Despite the many promising new anti-obesity drugs on the horizon, experts say there probably won't be any one "magic pill" for weight loss anytime soon. For right now, the best way to lose weight and keep it off is probably through old-fashioned diet and exercise.

For lots more information on the fat vaccine and related topics, check out the links on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links



  • Bryan, Jenny. "Could Fat be Catching?" Channel 4, March, 2005.
  • Coghlan, Andy. "Will the Fat Vaccine Help Dieters Shed Pounds?" New Scientist 186, May 21, 2005.
  • "Fat Jab Hailed a Success," Manchester Evening News, July 25, 2005.
  • Hawkes, Nigel. "Trials Start for a Vaccine Aimed at Fighting Obesity." Times of London, May 12, 2005.
  • Hitti, Miranda. "Study: New Weight Loss Drug May Help Dieters." WebMD, April 14, 2005.
  • Lister, Sam. "The Burger and Fags Jab." Times of London, August 13, 2005.
  • National Center for Health Statistics: Fast Stats.
  • "Noxxon Pharma AG and Merck and Co., inc. announce positive results with antighrelin spiegelmerĀ® in weight loss and obesity."
  • "Obesity Vaccine Enters Clinical Trial.", May 19, 2005.
  • CDC: Overweight and Obesity.
  • Selim, Jocelyn. "Science Takes on Supersize." Discover, September, 2005.
  • "Wonder Pill for Slimmers 'on the NHS Next Year." RedNova, April 15, 2005.