Vaccine prevents weight gain
Don’t get too excited by this – yet. The vaccine has only been studied in rats. But it appears to work. Here’s how.
Animals, including humans, have a protein hormone, called ghrelin. This hormone plays an important role in energy balance. Ghrelin levels go up when we try to lose weight and are suppressed in obese states. There is some evidence that elevation of ghrelin is an important driver that leads us to regain lost weight.
Ghrelin has a number of important actions that help the body keep energy stores (also known as fat) constant over long periods of time:
§ Ghrelin stimulates appetite
§ It decreases energy expenditure
§ It decreases the breakdown of stored fat
Mice that are deficient for ghrelin store less of their consumed food as fat and they resist accumulating body weight and fat on energy-dense diets.
Given this information, it makes sense that researchers interested in developing new approaches to address the obesity epidemic would target ghrelin. A report of one line of research appears in a recent edition of the Proceedings of the National Academy of Science (PNAS).
Eric Zorrilla and his fellow researchers developed a series of vaccines aimed at neutralizing the effect of ghrelin. Rats that responded with strong immunological activity against that hormone were compared to rats that were immunized with a weak vaccine or with a vaccine that had no activity against ghrelin.
Rats with a good antibody response to ghrelin gained less body weight compared to control animals. They also experienced a reduction in their body fat. Interestingly, the successfully immunized rats did not reduce their food intake. Rather, the effect seemed to be due to neutralizing ghrelin’s effects on energy metabolism.
There are still a lot of questions that must be answered via animal studies before a ghrelin vaccine will be tested in humans. Even after the vaccine is available for testing in humans, it can take years of research to determine if it is safe and effective as well as to understand how to use it properly.
That being said, what is so exciting about this line of research is not only the potential for new therapies, but also how it adds to our understanding of body’s complex control of appetite and body weight. There are a lot of folks who want to believe that obesity is purely a “personal responsibility” issue. But the more we learn about hormones, like ghrelin, the more we understand that weight gain is more than a personal choice. Rather, it is also the result of humans evolving to survive in a world where food was scarce and hard to come by, but now living in a world where energy dense food is always at our fingertips.
Who knows? It could turn out that people strongly driven by ghrelin to regain lost weight may require more motivation than other people to stay thin. And, people who are “naturally thin” may be luckier, not stronger, than people who tend to plumpness. Understanding these physiologic differences will, I believe, help us take blame out of the obesity field and lead us to focus on meaningful interventions tailored to an individual’s unique biochemical/behavioral profile. Now that is exciting.