The vaccine targets a hormone called ghrelin, which is responsible for preserving stores of body fat by decreasing expenditure of energy and reducing fat breakdown. Ghrelin acts as the body's protection against starvation by regulating appetite and metabolism depending on levels of food intake.
The researchers' vaccine tricks the body's immune system into attacking and destroying ghrelin -- much as it would attack bacteria -- by making the immune system believe ghrelin is a foreign body, thus preventing the hormone from reaching the brain, where its message to slow metabolism and store fat would prevent easy weight loss.
Mice injected with the vaccine experienced a 20 to 30 percent reduction in weight gain, though they were fed a low-fat, low-energy diet. The researchers are unclear whether the vaccine would work similarly with the unhealthy, fatty diet consumed by many obese Americans.
Critics of the "magic bullet" weight loss vaccine advocate a natural approach to weight loss involving healthy dietary changes and increased exercise. "Obesity isn't a disease," says Mike Adams, a prominent consumer health advocate. "This hyping of magic-bullet drugs helps no one and only distracts people from addressing the true causes of obesity: Diet and exercise."
With more than 64 percent of American adults either overweight or obese, natural health advocates say the only way to truly change the health of Americans is to change their behavior, rather than offer them an easy way out of the consequences of poor diet and exercise choices. "You don't solve the obesity problem by tricking the body into eating less of the same processed, nutritionally-depleted foods that dominate American diets," says Adams. "You solve the problem by teaching people how to make healthy food choices and adopt consistent exercise habits."