A group of researchers are contending obese kids may not be the result of lax parenting or a junk-food culture; obesity may have an infectious origin, according to a cross-sectional study by University of California, San Diego School of Medicine researchers who correlate children exposed to a particular strain of adenovirus, human adenovirus 36 (HAdV-36 or AD-36), being significantly more likely to be obese with some causation. 

Jeffrey B. Schwimmer, MD, associate professor of clinical pediatrics at UC San Diego, and colleagues examined 124 children, ages 8 to 18, for the presence of antibodies specific to adenovirus-36 (AD-36), one of more than 50 strains of adenovirus known to infect humans and cause a variety of respiratory, gastrointestinal and other infections. AD-36 has been the only human adenovirus linked to human obesity.

While an association between AD-36 and obesity in both animals and human adults has been previously described, the particulars remain poorly understood. For example, it is not known how often or under what circumstances AD-36 infects, why the virus affects people differently and whether weight gain is the result of an active infection or a lasting change in a person's metabolism.   In cell cultures, Schwimmer said, the virus infects pre-adipocytes or immature fat cells, prompting them to develop more quickly and proliferate in greater numbers than normal.

Slightly more than half of the children in the study (67) were considered obese, based on a Body Mass Index or BMI in the 95th percentile or greater. The researchers detected neutralizing antibodies specific to AD-36 in 19 of the children (15 percent). The majority of these AD-36-positive children (78 percent) were obese, with AD-36 antibodies much more frequent in obese children (15 of 67) than in non-obese children (4 of 57). 

Children who were AD-36-positive weighed almost 50 pounds more, on average, than children who were AD-36-negative. Within the group of obese children, those with evidence of AD-36 infection weighed an average of 35 pounds more than obese children who were AD-36-negative.

"This amount of extra weight is a major concern at any age, but is especially so for a child," said Schwimmer, who is also director of Weight and Wellness at Rady Children's Hospital in San Diego. "Obesity can be a marker for future health problems like heart disease, liver disease and diabetes. An extra 35 to 50 pounds is more than enough to greatly increase those risks."

Schwimmer said he hopes this research will help shift some of the burden that falls so heavily upon obese people, in particular children.   "This might be the mechanism for obesity but more work needs to be done."

The authors conclude: "These data support an association of obesity and higher body weight with the presence of neutralizing antibodies to AD36 in children. If a cause-and-effect relationship is established, it would have considerable implications for the prevention and treatment of childhood obesity."

Citation: Charles Gabbert, MD, Michael Donohue, PhD, John Arnold, MD, Jeffrey B. Schwimmer, MD, 'Adenovirus 36 and Obesity in Children and Adolescents', PEDIATRICS doi:10.1542/peds.2009-3362