Fat tax advocate and obesity researcher David Ludwig is at it again. He has published yet another study blaming fast food for childhood obesity — and once more we’re forced to ask: "Where’s the beef?" Ludwig told Bloomberg news that his study "raises concern that fast food could be an important cause of obesity." What his study actually found was that overweight teens tend to overeat, and leaner teens don’t. But this less-than-shocking conclusion didn’t stop Ludwig from offering — in the pages of JAMA (the Journal of the American Medical Association) — a leap of logic that would call on big government to regulate advertising: "Public health measures to limit fast food consumption in children may be warranted," he concludes, including "legislation to regulate marketing of fast food to children."
Ludwig’s paper was actually two studies in one. In the first, 13- to 17-year-olds were given hefty helpings of fast food, and when they were close to finishing, more was put in front of them — whether they asked for it or not. In Ludwig’s words:

Whenever approximately three fourths of the meal portion of chicken nuggets, fries, or cookies was consumed, a refill portion of the item was added to the tray. Empty cola containers were immediately replaced with full containers.

In this unrealistic scenario, it’s no surprise that all the kids ate quite a bit — with overweight children consuming 400 calories more than their normal weight peers. The second study asked teens to report what they had eaten during the previous 24-hour period. Here "energy intake was not significantly different on fast food and non-fast food days for the lean participants." Ludwig told one paper:

When the lean kids have fast food, they decrease their consumption of other foods by a precise amount, so their calorie intake on days with or without fast food are virtually identical.

In fact, Ludwig’s charts show that normal weight teens consumed fewer calories on the days they ate fast food (although the difference was not statistically significant). How Ludwig can take such a finding and still blame fast food for obesity is beyond us. Next thing you know, Ludwig will issue a press release declaring: "Earth Is Round! Study Suggests That Fast Food Culprit For Earth’s Rotund Shape!"
Think that kind of biased analysis doesn’t happen in prestigious medical journals? To illustrate scientists’ tendency to infuse obesity research with their personal politics, Dr. Glenn Gaesser of the University of Virginia gives his students a fascinating assignment. "I routinely take published papers and cut out everything but the methods and results, and have the students write a title, abstract, introduction, and discussion," he says. "You would be surprised at how differently the papers come out." It wouldn’t surprise anyone reading a Ludwig study that takes a small piece of common sense and then advocates government control. (Ludwig’s latest is actually the second peer-reviewed journal article he’s published this year advocating restrictions on food marketing without any justification.)
The National Institutes of Health (NIH), which funded Ludwig’s fast food study, presumably didn’t know that it was paying for policy advocacy. But the agency can only expect more of the same from two more (click here and here) Ludwig studies it’s currently supporting, both of which are investigating the supposed link between soda and childhood obesity. After all, NIH funded Ludwig’s 2001 study that tried to connect soda with childhood obesity, despite admitting that "there was no independent, significant association between baseline consumption [of soda by children] and obesity incidence."