Megan McArdle makes a number of striking and counterintuitive claims about obesity here to follow up on the striking and counterintuitive claims she makes here teaming up with Paul Campos, author of the interesting 2004 book The Obesity Myth. That said, whatever value this sort of thing may have as a kind of granscian intervention into the hegemonic media climate, I think it's all pretty irrelevant as an intervention in public policy disputes I'm familiar with.
For example, I would make the following claims about the idea of taxing soda and using the money to expand Medicaid and subsidize generous health insurance benefits for people in the bottom half of the income distribution:
— When you take into account not only the tax (which would be somewhat regressive) but also the services (which would be highly progressive) you have a progressive distributive impact.
— This would make soda more expensive.
— At the margin, the more expensive soda is the less people will drink of it.
— Drinking lots of soda is not healthy.
— Ergo, taxing soda to pay for health care expansion will mitigate income inequality and improve health outcomes both coming and going.
I don't see anything in what McArdle or Campos are saying to cast any doubt on that logic. Similarly, nobody seriously disputes that if it were legal to build more dense, walkable neighborhoods that more such neighborhoods would exist. Nor does it seem deniable that if more such neighborhoods existed, people would walk more. I don't see McArdle or Campos seriously denying that a lifestyle that includes some regular walking is healthier than a completely sedentary one.
Last, sophistry about how Megan's great-grandmother "knew that pound cake made you fat, and lettuce didn't" aside, I don't see how you can seriously deny that people would make healthier eating decisions if they had more accurate information at their disposal. Just today I was at a sandwich shop trying to choose between two sandwiches; they both sounded good and not-especially-healthy. My preference would have been to order the less-caloric of the two but I had no idea which one that was and this kind of thing happens all the time. Similarly, if we did less to subsidize the ingredients of pound cake and more to subsidize lettuce, I think it's fair to assume that people would eat somewhat less pound cake and somewhat more lettuce. And I'm pretty sure we all agree that pound cake is healthier than lettuce.
One can do this over and over again. I think there's decent Campos-style evidence that policy initiatives that amount to government hectoring of people about their wastelines is going to be at best useless. But there's much more to the policy world. The government provides lunch to tons of children, and determines what stuff is in their school's vending machines and apples are better for you than Fritos; baked potatoes are better for you than french fries.