The obesity explosion that has swept the Western world over the past 30 years may have been caused by a virus, scientists have said.
Researchers have discovered new evidence for an illness they have called "infectobesity" -- obesity that is transmitted from person to person, much like an infection. The agent thought to be responsible is a strain of adenovirus, versions of which cause the common cold.
There are more than 50 strains of adenovirus known to infect humans but only one, adenovirus 36, has been linked with human obesity.
Now scientists at the University of California, San Diego, have found that children who showed evidence of infection with adenovirus 36 were more likely to be fat. In tests on 124 children aged eight to 18, the virus was present in more than 20pc of those who were obese, compared with less than 6pc of the rest. Among those infected with adenovirus 36, four out of five were obese.
Children carrying the virus weighed on average almost 50lb more than those who were not. Among the obese children, who accounted for half the total, those with the virus weighed on average 35lb more than the rest.
Jeffrey Schwimmer, an associate professor of clinical paediatrics, who led the study published in the US journal Pediatrics, said: "This amount of extra weight is a major concern at any age, but is especially so for a child. Obesity can be a marker for future health problems like heart disease, liver disease and diabetes. An extra 35lb to 50lb is more than enough to greatly increase those risks.
"This work helps point out that body weight is more complicated than it's made out to be. And it is time that we move away from assigning blame in favour of developing a level of understanding that will better support efforts at prevention and treatment."
The idea of a viral cause for obesity was first raised a decade ago by Nikhil Dhurandhar.