Mounting evidence suggests obesity is contagious, scientists said today.
A human pathogen called the adenovirus Ad-37 causes obesity in chickens, according to a new study led by Leah Whigham of the departments of Medicine and Nutritional Sciences at the University of Wisconsin, Madison.
Previous research found that two related adenoviruses, Ad-36 and Ad-5, cause obesity in animals. Adenoviruses typically cause respiratory infections.
Importantly, Ad-36 has associated with human obesity in previous studies, and Ad-37 might be, too, but more research is needed, Whigham said.
"It makes people feel more comfortable to think that obesity stems from lack of control," Whigham said. "It's a big mental leap to think you can catch obesity."
And more work needs to be done.
"We still need to more definitively establish the link with these adenoviruses and human obesity," Whigham told LiveScience. "We also have no idea how the virus interacts with other factors such as diet and exercise."
The new findings are detailed in the January issue of the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology published by the American Physiological Society.
If obesity is contagious, the virus might be responsible for only part of the world’s growing girth. Changing diets, scientists say, surely also plays a role.
"The nearly simultaneous increase in the prevalence of obesity in most countries of the world is difficult to explain by changes in food intake and exercise alone, and suggest that adenoviruses could have contributed," the researchers conclude. "The role of adenoviruses in the worldwide epidemic of obesity is a critical question that demands additional research."
In an editorial in the journal, Frank Greenway, a professor at Louisiana State University, outlined some logical next steps for researchers.
"If Ad-36 is responsible for a significant portion of human obesity, the logical therapeutic intervention would be to develop a vaccine to prevent future infections," Frank said. "If a vaccine were to be developed, one would want to ensure that all the serotypes of human adenoviruses responsible for human obesity were covered in the vaccine."
The stakes are high.
"The prevalence of obesity has doubled in adults in the United States in the last 30 years and has tripled in children," the researchers write. "With the exception of infectious diseases, no other chronic disease in history has spread so rapidly, and the etiological factors producing this epidemic have not been clearly identified."
Richard Atkinson, also of the University of Wisconsin and a member of the research team, studied 500 obese people in 2004 and found that about 30 percent of them had antibodies to the Ad-36 virus, which suggests they may have been exposed to the virus.
As with any contagious disease, one line of defense would be to wash your hands. A study last year found that scrubbing with soap rids hands of most viruses in 10 seconds.