Certain Virus More Common in Obese People, but Expert Skeptical
But don't freak out just yet: Not all scientists are buying this theory.
The virus, called Ad36, is what's known as an adenovirus. Colds, flu, encephalitis, meningitis, and some cases of diarrhea are caused by adenoviruses, explains Richard Atkinson, MD, emeritus professor of medicine and nutrition at the University of Wisconsin at Madison.
"There are some 36 viruses that cause upper respiratory infections, some cause gastrointestinal problems, some cause inflammation of the brain," Atkinson tells WebMD.
Viruses can damage an organ, then disappear, he explains. "The polio virus leaves nerves damaged. Several viruses cause obesity in animals by causing inflammation and damaging the central nervous system. We don't think our virus does that."
Atkinson has led several investigations of Ad36 -- studies involving animals and humans. Published studies have shown that when the virus is given to chickens, mice, monkeys, and rats, their body fat increases by 50%-100% even though they ate the same amount as animals not given the virus.
"The virus seems to change body composition, so there is an increased percentage of fat," says Atkinson. "In monkeys, weight gain was about four times the weight gain of [comparison monkeys]." But there does appear to be some positive affect. Total cholesterol and LDL "bad" cholesterol levels go down, he says.
At two recent scientific conferences, he presented data on a study conducted in three U.S. cities involving more than 500 obese and normal-weight people who had their blood tested for antibodies to the Ad36 virus.
The results: About 30% of obese people had antibodies to this virus, compared with just 10% of normal-weight people. "If you have antibodies to the virus, you have been exposed. People testing antibody-positive were quite significantly heavier," Atkinson tells WebMD. This study will appear in an upcoming issue of the International Journal of Obesity.
If his results are true, then the virus could be part of this worldwide epidemic of obesity, says Atkinson. "It's reasonable that this virus is a contributing factor. ... Virtually everyone who gets this virus gains weight. It's a pretty robust phenomenon."