This is the third of 6 guest posts on infectious causes of chronic disease.
By Whitney Baker
While working out at the gym last night, I was perusing the latest SHAPE magazine to help pass the time. In it, I read a small article about researchers finding an association between Adenovirus-36 and human obesity. Since I am in the infectious disease field, I was already aware of this proposed link- an infectious cause (or contributor) for obesity. But for the millions of health-conscious readers hearing of this for the first time, what would they make of it? Would they have visions of medicines or vaccines that make them skinny? Would they think that diet and exercise no longer matter? Luckily mainstream media hasn’t started a commotion over this. But it did get me to wondering, that if there really is a link, what accountability is then transferred to the media? Reports of a looming “skinny shot” could have a detrimental affect by spawning false impressions of health and fitness, especially for those most vulnerable to obesity.
(More after the jump…)
Quite a few peer-reviewed articles have addressed the issue of infectious obesity. Experts say that the obesity epidemic has an etiology epidemiologically analogous to an infectious origin because of its rapid spread worldwide. Obesity has increased significantly since the early 80s, and not just in the US, but in both developed and developing countries. And, to my surprise, not just Adenovirus-36 has been implicated as a culprit to America’s bulging waistline. A 2007 review paper by Richard Atkinson discussed 5 animal viruses (canine distemper virus, Rous-associated virus type 7, Borna disease virus, scrapie agent, and an avian adenovirus, SMAM-1) and 3 human viruses (adenovirus (Ad) 36, Ad-37, and Ad-5). Another 2007 review by Vasilakopoulou and Roux delineated these same pathogens in their review as well. All 8 of these viruses could be linked to the obesity epidemic. A 2007 seroepidemiological study by Thjodleifsson et al. studied individuals in Iceland, Sweden, and Estonia for IgG antibodies against Helicobacter pylori’s cagA protein, hepatitis A virus, Toxoplasma gondii, herpes simplex virus 1, Chlamydia pneumonia, Epstein-Barr virus, and cytomegalovirus. The researchers found a significant association between being overweight and being infected with H. pylori or C. pneumoniae, and a combined seropositivity of these two had a synergistic effect. Adenovirus-36 (which was not a target in the aforementioned seroprevalence study), was recently shown to play a role in adipocyte (fat cell) differentiation. Ad-36 can take adult stem cells and transfer them into fat cells (adipogenesis), thus contributing to the world’s expanding waistline.
So with that said, I suppose SHAPE magazine wasn’t too far out there in reporting on the story. Evidence seems to support an infectious component to obesity. But what about the weight-loss industry being such big hitters and people looking for the “quick fix” and falling for the latest fad diets or the miracle pill? The FDA estimates Americans spend an estimated $30 billion dollars on diet programs and products each year, and 50 million Americans will go on a diet this year. They’ll invest in anything that has a promise of a brighter– and skinnier– future. With so many gullible Americans out there, what are the consequences of informing people that they may be fat because of an infectious disease? I can see it now- late night infomercials selling medicine to cure the “disease”. You know, Kevin Trudeau, the infomercial guy who first came on the scene for something like real estate or making money fast, then all of a sudden lost a lot of weight and became an expert on natural cures for disease and even wrote several books. I can see him now… trying to tell Americans what the government doesn’t want them to know. Obesity is an infectious disease! And with this pill, it’s curable! Oh my…
But perhaps infomercials are at the far end of the spectrum and probably don’t even count as a media outlet. So imagine Fox News or CNN getting a hold of this story on a slow news day, and making consumers wonder when they can get vaccinated against the obesity bug. We all know the media is not known for providing ALL the facts; they go for the dramatic, captivating headlines. They’re not going to say there “may” be a link and an infectious agent “may” be a contributory factor to gaining weight. They’re not going to highlight that there is still a strong behavioral component to obesity, and most likely diet and exercise are the best ways to be healthy and to slim down. No, they’ll go for the attention grabber. And in return, a number of people (those who donate to the weight-loss industry in particular) might have visions of “cure me” rather than taking personal responsibility for where they are at and how they got there.
With the available data, it seems like an infectious agent does contribute to obesity. It is an attractive concept, as many chronic diseases have squashed long-standing opinions and are now recognized to have infectious etiologies (e.g. H. pylori and peptic ulcers, the human papillomavirus and cervical cancer, and the hepatitis B virus and liver cancer). More and more, pathogens are being implicated, so it doesn’t seem like a stretch to make a link to obesity. But for as long as the culprit remains unidentified and the model of pathogenesis a mystery, the theory of an infectious cause to the obesity epidemic should remain in the scientific field. Consumers are too eager, too desperate, and too amateur. The media should take care to not flaunt the idea of a “skinny shot”. Because even if you get rid of the fat cell-generating Ad-36, being a couch potato and having a Big Mac, large fries, and a shake every day is going to do way more damage to your health (and to your waistline) in the long run.
Whitney has been interested in infectious diseases since the 8th grade. She has a Bachelor’s in microbiology and a Master’s in Public Health in epidemiology. Two years after landing a university job in infectious disease epidemiology research, she began working toward a PhD in epi. Whitney’s focus area is emerging zoonotic diseases- in particular, the epi of cross-species pathogen transmission from animals to humans- but she has no idea what she’ll do when she’s no longer in school.
Atkinson RL. Viruses as an etiology of obesity. Mayo Clinic proceedings 2007;82(10):1192-8. PubMed link.
Vasilakopoulou A, le Roux CW. Could a virus contribute to weight gain? Int J Obes (Lond) 2007;31(9):1350-6. Link.
Thjodleifsson B, Olafsson I, Gislason D, Gislason T, Jogi R, Janson C. Infections and obesity: A multinational epidemiological study. Scand J Infect Dis 2007:1-6. Link.
Pasarica M, Mashtalir N, McAllister EJ, et al. Adipogenic Human Adenovirus Ad-36 Induces Commitment, Differentiation and Lipid Accumulation in Human Adipose-derived Stem Cells. Stem Cells. 2008. Link.
Rogers PM, Fusinski KA, Rathod MA, et al. Human adenovirus Ad-36 induces adipogenesis via its E4 orf-1 gene. Int J Obes (Lond) 2007. Link.
Image from http://metabolism.com/images/dreamstime_1868442obese.jpg