Image caption How the AD36 virus infects people and why it affects people differently is not known

A virus which causes respiratory infections has been linked to childhood obesity, in a study that is likely to reignite a controversial debate.

Previous animal research has implicated common viruses in weight gain, but the evidence has been disputed.

The latest study, in Pediatrics, found that obese children with antibodies specific to a certain virus weighed 35lbs (15.8kg) more than those without.

Nothing has yet been proven on this theory, say UK experts.

Previous research has shown that chicken or mice injected with similar types of viruses showed a statistically significant weight gain.

A link between the AD36 virus (adenovirus 36) and obesity in human adults has also been written about previously.

But how AD36 infects people and why it affects people differently is still not known.

Antibodies found

In the University of California study of 124 children aged eight to 18, half of the children were considered obese based on their Body Mass Index.

The study does add a little evidence to suggestions that AD36 may be implicated in some way with childhood obesity. Prof Julian Hamilton-Shield, University of Bristol

The researchers found the AD36 antibodies in 19 of the children, 15 of whom were in the obese group.

Within the group of obese children studied, those with evidence of AD36 infection weighed an average of 35lbs more than obese children who were AD36-negative, says the study.

Jeffrey Schwimmer, lead researcher and professor of clinical paediatrics at the University of California school of medicine, said he hoped his research would change attitudes to obese people.

"Many people believe that obesity is one's own fault or the fault of one's parents or family. 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 both prevention and treatment.

"These data add credence to the concept that an infection can be a cause or contributor to obesity," he said.

Julian Hamilton-Shield, professor in diabetes and metabolic endocrinology at the School of Clinical Sciences, University of Bristol, says the jury is still out on this idea.

"It's an interesting if small and non-definitive study. This does not show causation, just an association.

"For instance, it may be that obese people are at more risk of catching AD36.

"However, it does add a little evidence to suggestions that AD36 may be implicated in some way with childhood obesity," he said.