Jeff Schwimmer and his University of California-San Diego colleagues seem to think so. In a press-release that is being cut-and-pasted across across the internet, Schwimmer tells of a study he conducted which appeared to show that kids who caught a cold from the adenovirus 36 (AD36) were fatter than kids who avoided that virus.
To understand this study, you must become savvy to the lingo pediatricians use. Foremost is their use of the word children. Say that word to most civilians and they conjure up images of pre-teens; but to a pediatrician it implies anybody under 19, and sometimes even under 22. There is nothing wrong with this, of course, but if you were unaware of the distinction while examining pediatric study results, you could easily fool yourself.
Schwimmer et alia “examined 124 children, ages 8 to 18, for the presence of antibodies specific to” AD36. They also measured these kids’ weight, height, ethnicity (two-thirds were Hispanic; one quarter white; a tenth black), sex (just over half were boys), and so forth. But why look for previous infections of the AD36 virus? According to the press release:
While an association between AD-36 and obesity in both animals and human adults has been previously described, the particulars remain poorly understood. For example, it is not known how often or under what circumstances AD-36 infects, why the virus affects people differently and whether weight gain is the result of an active infection or a lasting change in a person’s metabolism. In cell cultures, Schwimmer said, the virus infects pre-adipocytes or immature fat cells, prompting them to develop more quickly and proliferate in greater numbers than normal.
In other words, some suspect that, through an inexactly specified and largely unknown mechanism, the virus makes people pack it on. Of course, the virus also might have nothing to do with weight gain.
Half the kids (67) in the study were “obese” as specified through the problematic body mass index (BMI; which over-classifies actual obesity). Fifteen-percent (19) of the kids were found to have been previously exposed to AD36, and 78% percent of those exposed were obese. That is, 15 out of the 124 total kids were both exposed to the virus and were said to be too fat.
I cannot be more specific about the numbers because although the press release promised the paper would in the 20 September on-line version of Pediatrics, I could not locate it.
The main finding is that kids “who were AD-36-positive weighed almost 50 pounds more, on average, than children who were AD-36-negative.” Findings of this kind usually imply that the distribution of weight in the two groups is identical, except that the mean of the exposed group is higher. This is a strong assumption and is usually only met approximately, if at all. But never mind: the study had a statistician, and we can assume he made the proper adjustments for deviations from this assumption (such as for ethnicity).
However, the one measure that cries out for adjusting is age. Just think: exposed kids are on average 50 pounds heavier—50 pounds! That’s an enormous difference! Why, it’s the same difference in weight as between the average 18-year-old and average 9-year-old. And, say, this study had 18- and 9-year-old kids, didn’t it?
Now, what if it was the older kids who predominated in the group exposed to AD36? Then it would falsely appear that exposure leads to weight gain. Importantly, older kids have obviously had more time to be exposed to the virus. The small number of kids and their wide range of ages in this study could easily lead to a false signal.
What’s more plausible: kids who are exposed to a virus plump up, or that sedentary fat kids catch colds easier than their lither compatriots? That is, Schwimmer might have it backwards: obesity might cause colds!
There is also some indication that Schwimmer had a desire that the study show that AD36 causes obesity. From the press release:
What Schwimmer does hope the findings will do is get people to “move away from assigning blame, and broaden the way we think about obesity. Currently, there’s a somewhat simplistic belief that obesity is just a person’s own fault, or in the case of children, the fault of the family. But, that’s an overly simplistic view, and it’s not helpful,” he said.
Rephrasing: it’s not the kids’ fault that they’re fat. Sitting on their keisters for endless hours in front of a glowing screen is less plausible as a cause of obesity than is a virus working through mysterious means. Further, it is not helpful to yell that kids should turn off the damn computer/TV/video game, stop shoving so much cake down their pie holes, and get outside.
Thanks to reader and contributer Ari Schwartz for suggesting this topic.
Update Thanks to reader and soon-to-be contributer Katie who has tracked down the paper (it was not where we had supposed).
The data indicated that for the AD36 Negative group, the ages were 8-11 yrs (18%), 12-15 yrs (65%), and 15-18 yrs (17%). For the AD36 Positive group, the ages were 8-11 yrs (5%), 12-15 yrs (32%), and 15-18 yrs (63%). This is as we surmised above: more older kids are in the AD36 group. The weight average for the AD36 Negative group was 69 kg (+/- 24 kg SD); for the AD36 Positive group is was 93 kg (+/- 24 kg SD).
Thus, one sure finding is that older kids are heavier: in fact, they were about 24 kg heavier, which translated to about 50 lbs. It is at least good to see that the press release got this figure correct.
Another finding is that older kids are more likely to have been previously infected by AD36, also as we surmised (in two years, you have have plenty of colds).
There was no word in the paper that the authors adjusted for age. Indeed, there were no limitations of any kind mentioned.