A very interesting article over at Science Blog talks about the possibility that obesity may be caused by adenoviruses, at least in part:
“It makes people feel more comfortable to think that obesity stems from lack of control,” Whigham said. “It’s a big mental leap to think you can catch obesity.” However, other diseases once thought to be the product of environmental factors are now known to stem from infectious agents. For example, ulcers were once thought to be the result of stress, but researchers eventually implicated bacteria, H. pylori, as a cause.
“The nearly simultaneous increase in the prevalence of obesity in most countries of the world is difficult to explain by changes in food intake and exercise alone, and suggest that adenoviruses could have contributed,” the study said. “The role of adenoviruses in the worldwide epidemic of obesity is a critical question that demands additional research.”
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The theory that viruses could play a part in obesity began a few decades ago when Nikhil Dhurandhar, now at Pennington Biomedical Research Center at LSU, noticed that chickens in India infected with the avian adenovirus SMAM-1 had significantly more fat than non-infected chickens. The discovery was intriguing because the explosion of human obesity, even in poor countries, has led to suspicions that overeating and lack of exercise weren’t the only culprits in the rapidly widening human girth. Since then, Ad-36 has been found to be more prevalent in obese humans.
In my case I’m pretty sure it’s the fact that I eat more than I should and I don’t exercise much beyond hauling my ass up and down the basement steps to get to my computer, but I’m not as heavy as some of the folks in my family are either. The article goes on to point out that the evidence is still sketchy at best and there’s still a lot of work to be done before they can say anything conclusive one way or the other, but there’s certainly some indication that this is a theory worth pursuing especially if a vaccine could be developed to counteract it. This would go a long way to explaining why there are some folks have tried dozens of diets and exercise programs and ended up with only marginal weight loss.
Posted on 01/31/2006 at 01:24 PM 
Very neat. I was always on the opposite end, and excuses for my body were never demanded - I ate what I wanted, never excercised. Yet I had a slender, muscular body and the immune system of an ox. People never gave me the “get in shape” thing, they just said “oh, some people are like that”, when I popped the question as to why my body was the way it was. It always made me wonder if we weren’t inadvertantly dismissing something important. It just seemed so presumptuous; like, we have the answers when it comes to one body and not to the other on the opposite end of the scale.