Are Ex-Smokers Even More Likely to Gain Weight Than Previously Thought?

We’ve blogged several times here about the rise in American obesity and its various causes. From one of those earlier posts:

Why has the U.S. obesity rate risen so much? Many, many answers to this question have been offered, most of them having to do with changes in diet and lifestyle (and, to some degree, the changing definition of “obese”). There is an interesting paper by the economists Shin-Yi Chou, Michael Grossman, and Henry Saffer that sorts through many factors (including per capita number of restaurants, portion sizes and prices, etc.) and concludes — not surprisingly — that the spike in obesity mostly has to do with the widespread availability of very cheap, very tasty, very abundant food. They also find that a widespread decline in cigarette smoking has helped drive the obesity rate. This seems very sensible, since nicotine is both a stimulant (which helps burn calories) and an appetite suppressant. But Jonathan Gruber and Michael Frakes have written a paper that calls into doubt whether a decrease in smoking indeed causes weight gain.

So does smoking less lead to weight gain or doesn’t it?

A new paper (gated) in the International Journal of Obesity argues that not only does smoking less lead to weight gain, but that the effects have to this date been underestimated — primarily because, as Michael Finke, one of the authors, explains, “smokers are not like nonsmokers.”

From the introduction of their paper:

Adult obesity rates in the United States have increased by more than 50 percent, whereas tobacco use among adults decreased by about 44 percent since 1970. There is strong evidence that smoking is inversely related to body mass index (B.M.I.). However, smokers tend to consume diets that are higher in fat and lower in nutritional quality than nonsmokers. Smoking and unhealthy diet choice may reflect a preference for the present consumption. Smokers appear to exhibit a higher rate of time preference through myopic decision-making in multiple domains. If smokers are more present-oriented, and if activities such as healthy diet and exercise require placing a greater value on future well-being, it is possible that the past estimates of the relation between smoking and B.M.I. suffer from an omitted variable bias. This study attempts to correct this bias by including time preference through the use of a composite index of behaviors that reflect a preference for either future or present well-being.

This argument has a lot in common with several arguments we put forth in Freakonomics: that the kind of person more likely to do X is also more likely to do Y.

Humanists may find this unsettling: it is perhaps more comforting to think that our individual choices are, well, individual. But the empirical evidence continues to point in the other direction.