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The Obesity Virus? RESEARCHERS SUGGEST VIRAL INFECTION MAY CAUSE OBESITY

DOC News January 1, 2005
© 2005 American Diabetes Association

The Obesity Virus?
RESEARCHERS SUGGEST VIRAL INFECTION MAY CAUSE OBESITY

Nick Kolakowski

Could obesity be due, at least in part, to a viral infection? The idea may seem farfetched, but then so was the idea that peptic ulcers are caused by bacterial infection.

A group of researchers have implicated the adenovirus Ad36—one of a family of about 50 viruses that cause colds, upper respiratory infections, gastrointestinal problems, and eye inflammations—in the development of obesity in humans and other animals.

At least six pathogens are suspected of causing obesity in animals, including canine distemper virus, an avian retrovirus, Borna disease virus in rats, and the scrapie agent in mice and hamsters.1

In 1992, Nihil V. Dhurandhar, PhD, then at the University of Bombay, India, reported on the avian adenovirus SMAM-1, which caused excessive intra-abdominal fat deposition and paradoxically low serum cholesterol and triglyceride levels in chickens.2 Antibodies against SMAM-1 virus were found in 10 of 52 humans with obesity screened in Bombay. Those people with antibodies had a significantly higher body weight and body mass index (BMI).3

According to Richard Atkinson, emeritus professor of medicine and nutrition at the University of Wisconsin at Madison, animals infected with the Ad36 virus have a 50% to 100% gain in body fat. When Atkinson, Dhurandhar, and colleagues screened humans for specific Ad36 antibodies, they found that around 30% of the people with obesity had the antibodies, compared with 10% of the normal-weight people.

“We can’t say that the virus caused obesity in all those people,” Atkinson says. “It’s still speculation, some say a gross speculation.” Yet the research and its implications have led him to set up the Richmond, Va.–based Obetech Obesity Research Center, where people can pay for testing to see if their extra pounds are caused by pizza or pathogen.

ONGOING RESEARCH

Because of restrictions on human testing, Atkinson, Dhurandhar—now at Wayne State University in Detroit—and colleagues have limited research to mice and monkeys. Studies show that animals inoculated with the virus gain weight even as their food intake remains the same. Research also suggests that Ad36 is transmissible from animal to animal.

“Our animal experiments showed that the virus could be passed from one infected animal to its cage-mate within 12 hours of infection,” Dhurandhar says. “Also, blood from the infected animal, injected in the veins of a fresh set of animals, transmitted the virus and obesity.”

If a virus is involved at all in the development of obesity, no one is suggesting it is the sole cause. Obesity is the result of a number of factors, some genetically based and others that are environmental.

Other researchers think that the virus isn’t much of a factor in the nation’s expanding waistlines. Cardiologist Thomas Kottke, MD, of Regions Hospital Heart Center in St. Paul, Minn., says that trying to blame the obesity epidemic on a virus is avoiding reality. “It’s like saying, `I don’t need to quit smoking because by the time I get lung cancer there’ll be a cure,’” he says. “And there’s no cure, and it kills 85% of the time.”

Instead, Kottke believes the answer to the obesity epidemic is right in front of us: people are consuming more calories than they’re using. “We don’t have to get off our butts to change the channel, the cost of food is at record lows, and there are cities all over that are impossible to walk in.”

Other doctors and researchers give the idea of an obesity virus slightly more credibility. “It is a possibility that some people might be affected by a virus,” says F. Xavier Pi-Sunyer, MD, director of the Obesity Research Center at St. Luke’s-Roosevelt Hospital in New York City. “You’ve got to postulate that somehow [the virus] is getting into the brain and affecting the brain centers and somehow affecting appetite.”

The possible role of Ad36 “is an interesting observation, but I would not give high priority to these problems,” says Pi-Sunyer. “I think the main cause of our obesity problem is that we eat too much.”

TESTING AND IMPLICATIONS

Atkinson thinks Obetech’s test for Ad36 antibodies will be important for people suffering from overweight or obesity. “Obese people really suffer an immense amount of discrimination, they’re told they’re lazy and that it’s a character flaw,” he says. “If it’s a virus, that puts a whole new spin on things. They’d feel a whole lot better.”

“But the more important use of this test will be for skinny people,” Atkinson continues. “If you’re skinny and your test is positive, it means you have a good chance of becoming obese due to this virus. It’s easier to prevent obesity than to change or reverse it.” Atkinson’s hope is that more people will eventually “want to know their obesity virus status.”

In the long term, the identification of a virus responsible for some incidence of obesity may lead to more clinically relevant screening tests, perhaps a vaccine or antiviral therapy, and a greater acceptance of obesity as a disease.

References

1. Dhurandhar NV: Infectobesity: obesity of infectious origin. J Nutr 131 (Suppl.):2794S –2797S, 2001.[Abstract/Free Full Text]
2. Dhurandhar NV, Kulkarni P, Ajinkya SM, Sherikar A: Effect of adenovirus infection on adiposity in chicken. Vet Microbiol 31:101–107, 1992.[Medline]

3. Dhurandhar NV, Kulkarni PR, Ajinkya SM, Sherikar AA, Atkinson RL: Association of adenovirus infection with human obesity. Obes Res 5:464–469, 1997.[Abstract]

The Obesity Virus? RESEARCHERS SUGGEST VIRAL INFECTION MAY CAUSE OBESITY