Are the Obese Weighing Down Health Care?

The idea that fat people are driving up health care costs is one of those arguments that's so easy to make and so thinly intuitive that I almost resist believing it, out of reflexive skepticism. But I was interested to read, via The Curious Capitalist, that the U.S. Department of Health and Human Services has data showing that recently health care costs for heavier people people are rising much faster than for the rest of us.

How much faster? Ezra Klein is kind enough to graph these increases so we can compare with our eyes. The Y-axis indicates "percent rise in health expenditures for people categorized as [normal, overweight, obese]:"
Unsatisfied with a feeding readers with a meager graph, Ezra stuffs his analysis with a heaping portion of caveats:

That data, which comes from the Agency for Healthcare Research and Quality, looks a bit more straightforward than it necessarily is. You're not just seeing sicker individuals in there. You're also seeing the financial incentives of overtreatment, the advance of medical technology, a lot of wasteful interventions, a system that overspends for every unit of care purchased, and so on and so forth. You're also seeing demographic correlations: Obesity is a particular problem among poor and minority communities, both of whom tend to be sicker.

There are a lot of things going on here. One the one hand, it's extremely difficult to tease out the specific effect of obesity on health care spending, because we don't know whether that obesity is going to result in a long-term illness or a very quick death. Treating decades of diabetes is much more expensive than treating a heart attack. You can say that one way to reduce the demand for more health care is just to be more healthy in the first place. But a perfectly fit person can develop another kind of long-term ailment that requires expensive treatment and his fitness might prolong his life, and therefore increase the cost of his treatment. At the end of the day, there are plenty of good reasons to encourage folks to live lives of utmost healthiness. Health care costs might be one of those reasons, but I'm not sure it's the best one.