The Scripps Research Institute scientists in La Jolla, Calif., conducting the study and testing on rats, said mature male rats immunized with specific types of the active vaccine ate normally, yet gained less weight and had less body fat, "indicating that the vaccine directly affects the body's metabolism and energy use."

    The vaccine targeted ghrelin, a hormone discovered in 1999 that helps control appetite in animals and people.

    According to the scientists, during periods of weight loss, such as dieting, the body produces high levels of ghrelin to slow down fat metabolism. This encourages eating and promotes fat retention.  

    But the scientists found the new vaccine will keep more ghrelin circulating in the blood and less from reaching the brain and the central nervous system, gradually increasing the rats' use of energy and allowing them to add less body weight and fat.

    The finding, said the scientists, might be particularly important to stop "yo-yo dieting," the cycle of repeated loss and regain of weight experienced by many dieters.

    "The study shows our vaccine slows weight gain and decreases stored fat in rats," said Kim Janda, a professor of chemistry at the Institute, senior author of the research report. 

    However, the scientists cautioned that such a vaccine is a long way from being tested in human volunteers, and that it may not work in people. "We're not claiming that our study answers the question of obesity treatment once and for all," Janda said. "What we are saying, and what our study confirms, is that this looks like a serious workable solution to the problem."

    Janda said, "We could speed quickly into human trials, maybe in a year, but we are going to be more cautious." Enditem

    (Agencies)