Jan 26, 2009
Catching Obesity
UPDATED: Is it possible that obesity, like the common cold is infectious? You’d think so if you believed research that’s been carried out over the last decade and hits the tabloid headlines again this week.
The research suggests that a highly infectious virus might be behind some cases of obesity. There is constant talk of an epidemic of overweight in the developed world. Overindulgence, lack of exercise, sedentary lifestyles are usually blamed. Occasionally, the words genetics or glands are mentioned, but rarely is the obesity epidemic thought of as a disease like, flu or winter vomiting virus, a disease you can “catch”, in other words. But, this research detracts from those genuine causes of overweight and might even do more harm than good, giving those with a less than healthy appetite another excuse to over indulge and avoid raising their heart rate above the average.
The research is highlighted today in several UK news papers and apparently lends weight to the idea that a highly infectious cold-like virus, known as AD-36 could cause obesity in some people.
It’s perhaps not surprising that, aside from the Daily Telegraph, most of the other outlets that report this work without real commentary are tabloids, the Daily Express, the Daily Mail, and Fox News, for instance. The original research is by Nikhil Dhurandhar of the Pennington Biomedical Research Centre in Louisiana and colleagues and will also be highlighted on the supposedly reputable BBC Horizon TV program this evening in an episode that attempts to answer the question, Why are thin people not fat?
Dhurandhar’s answer to that question is that those people simply haven’t yet caught the obesity bug. Apparently, the “virus goes to the lungs and spreads through the body. It goes to various organs and tissues such as the liver, kidney, brain and fat tissue…causes fat cells to replicate.” Moreover, the team’s latest paper published 22nd January 2009 in the journal Obesity, suggests that fat cells, known as 3T3-L1 cells, accumulate fat molecules (lipids) faster than normal when a person is infected with AD-36.
None of this is new, however. Dhurandhar and colleagues have been searching for an obesity “bug” for at least a decade. They published preliminary results in 1996 and 1997 and since then have apparently tested their theory in chickens, mice and marmosets. My good friend Tabitha Powledge wrote about the theory back in 2000 for Salon). Dhurandhar’s work on the viral theory of obesity also hit the news in the summer of 2007 when he reported details to the 234th national meeting of the American Chemical Society. At the time, the studies revealed that almost a third of people with obesity were infected with the AD-36 virus compared to just over one in ten of lean individuals. But does the presence of such a virus truly imply some obesity is due to catching an infection?
Last year, R.L. Atkinson of the Obetech Obesity Research Center, in Richmond, Virginia, reviewed the field and concluded that, “a portion of the worldwide epidemic of obesity since 1980 could be due to infections with human adenoviruses” (Int J Pediatr Obes. 2008;3 Suppl 1:37-43). More recently, Dutch researchers Vincent van Ginneken, Laura Sitnyakowsky, and Jonathan Jeffery, discussed Dhurandhar’s work in the journal Medical Hypotheses and agree with the findings: “We postulate that AD-36 may be a contributing factor to the worldwide rising problem of obesity,” they say, “We suggest the extension of comparative virological studies between North America and Europe, and studies between discordant twins (both dizygous and monozygous).”
The key phrases are “could be due” and “may be a contributing factor”.
It is very unlikely that, even for a proportion of individuals, will the viral theory prove to be the cause of their obesity. This is not the straightforward case we saw with peptic ulcers and the discovery of Helicobacter pylori. Even the link between gum disease bacteria and heart problems, while tentative, is more substantial.
It’s ironic that this research should come to the fore (again) within a week of the European Union giving the go ahead for pharmacists to sell the obesity drug Orlistat over the counter (OTC).
It is possible that for a small number of people the best defence against obesity would be to avoid catching this so-called obesity bug? Best way to avoid bugs? Enjoy a good diet, do not overindulge, and get plenty of fresh air and exercise and perhaps follow the how to avoid colds and flu tips too. Good nutrition, moderation and exercise will cover you for the biggest obesity risk factors, boost your immune system to a degree, and help you avoid adenoviruses infection. It’s a well-padded strategy, I’d say.
Miloni A. Rathod, Pamela M. Rogers, Sharada D. Vangipuram, Emily J. McAllister, Nikhil V. Dhurandhar (2009). Adipogenic Cascade Can Be Induced Without Adipogenic Media by a Human Adenovirus Obesity DOI: 10.1038/oby.2008.630
Yes, if a mechanism could be revealed that could be very useful. Thanks for spotting that badly edited sentence re antivirals, it was inadvertent.
I’ve looked at the papers on this issue, and there is no doubt that AD36 is adipogenic in cell culture, and in certain animals can cause weight gain. What needs to be done is to identify the mechanism by which the virus induces the adipogenic program. If it’s real, then a mechanism will be identified and can be used to test the model in animals. If this work is fruitful, then we need a comprehensive epi study to determine association with infection. If cellular targets of AD36 are identified then these should be examined in people as well (eg for polys associated with disease).
One nit-pick, David, please reserve the use of ‘antibiotics’ for bacteria. For viruses, use the term ‘antiviral’. As you know antiviral can be highly effective. Your sentence “Viral infections do not succumb to antibiotics anyway, (in fact bacteria often don’t either), so an antiviral diet pill is unlikely” is a bit confusing as a result (not to me, to the general public).
obesity is infectious? http://tinyurl.com/dc5u5n
Indeed, that’s exactly what the Horizon producers demonstrated with a group of young people. They tried to fatten them all up over the course of four weeks by doubling their calorie intake and precluding exercise. They were all fairly slim to start with and none of them got particularly fat, they all reverted to “type” within a couple of weeks of the “experiment” ending.
The news on this claimed he was seeing 30% infection in overweight individuals tested, but on BBC Horizon he said 20%, so it’s not even as strong a correlation as the original hyperbole over the last 10 years has had it.