Researchers are trying to develop a vaccine that suppresses ghrelin -- a hormone secreted by the gut into the blood that acts on the brain to stimulate appetite.
Eating more calories than you expend is an important cause of obesity. In fact, regardless of your genetic predisposition to obesity or your resting metabolic rate, you cannot gain weight without consuming more calories than you burn.
To point to overeating as the cause of obesity is overly simplistic, however. It does not explain why a 125-lb woman can eat 1,800 calories a day and not gain weight, while another 125-lb woman struggles to avoid gaining weight on 1,200 calories a day. This difference occurs because numerous other factors contribute to weight gain, including resting metabolic rate and physical activity. Nevertheless, obese people must be consuming more calories than required by their individual make-ups and activity levels. Otherwise they would not store excess body fat. Thus, if you’re overweight, you must reduce your calorie intake to lose weight.
Now there’s promising news for people struggling to keep weight under control: Researchers are trying to develop a vaccine against obesity using antibodies to the appetite-stimulating hormone ghrelin. The obesity vaccine shows promise in rats, according to a recent study reported in the Proceedings of the National Academy of Sciences (Volume 103, page 13226).
Ghrelin is a hormone secreted by the gut into the blood that acts on the brain to stimulate appetite. In rats, the hormone also decreases energy expenditure and slows the breakdown of fat. But rats deficient in ghrelin or lacking a receptor for the hormone store less of the food they eat and fail to gain weight when placed on a high-calorie diet.
In the study, the researchers prepared three different antibodies to ghrelin and tested them in 17 male rats as a possible vaccine against weight gain. The vaccinated rats were allowed to eat as much as they wanted, but the rats given two of the three vaccines gained less weight, maintained muscle mass, and lost body fat compared with the control mice. The third vaccine was ineffective.
Although the results are encouraging, the research is preliminary. And just because something works in rats does not mean that it will have the same effect in humans. In fact, in humans (especially obese people) appetite is not the only trigger to eat -- emotions, habit, and stress, for example, also play a role -- so a vaccine that quenches appetite may not have significant or lasting benefits in humans.
