Harvard economist David M. Cutler jumps on the sugar-tax boat this morning in an opinion piece in The Wall Street Journal. Arguing that the Obama health-care reform program is worth salvaging because it will help flatten the medical inflation curve, he nevertheless faults the proposals for lack of nutrition-sin taxes. The program “provides new incentives for physicians to focus on preventive and chronic care and opens Medicare to finding new ways of supporting prevention,” he writes. “The only area of weakness is the lack of a junk-food tax or a tax on sugar-sweetened beverages. Grade: Partial credit.”

Cutler’s remarks come right on top of new research published in the Archives of Internal Medicine yesterday (covered here by Reuters) claiming that a tax on soda and pizza could be an effective weapon in the campaign against obesity. This was one massive study; the researchers took their data from more than 5,000 young adults over 20 years. The upshot: They estimate that an 18 percent tax could result in weight loss of 5 pounds per person per year.

This came as a shock to me, not only because of the implied threat to my Friday night large pepperoni with spicy sauce, but also because the last bit of actual research (as opposed to opinion-spouting) that I saw on this topic pointed in the opposite direction. In a paper called “Can Soft Drink Taxes Reduce Population Weight?” published last summer, researchers Jason M. Fletcher, David Frisvold, and Nathan Teff noted that sugary drinks represent only 7 percent of total energy intake. “Therefore, we should expect only modest changes in population weight through soft drink consumption responses to small tax increases.” Even a relatively large tax increase, say 20 percent, “may not have a substantial effect on population weight.” (Read a summary or download the whole thing here.)

So … who you gonna believe? For now, I’m going to assume that the tax/nutrition wonks are not getting consistent results. Until they do, you politicos, keep your tax knives out of my pizza! ###