A favorite the-sky-is-falling claim of anti-food crusaders like Twinkie tax godfather Kelly Brownell and David Ludwig is, “Children will have a shorter life expectancy than their parents.” We have been suspicious of that assertion ever since it was made by activists in Congressional testimony in 2002 and by the authors of a 2005 New England Journal of Medicine article, and a new study by economists from the University of Pennsylvania Population Studies Center and Emory University gives us even more evidence to dismiss the hyperbole.

The economists, who published their research in a National Bureau of Economic Research working paper, analyzed the effects of increased obesity and reduced smoking on life expectancy from age 40 onwards through 2040. They found that life expectancy gains from reduced smoking — which other research has linked with weight gain — completely outweigh life expectancy losses from obesity-related disease. In this analysis, men are expected to gain a little less than one year after age 40, and women (who have higher life expectancies) gain about one-quarter of a year. The researchers did not assess other factors, like what effects improved future medical treatments might have.

These projections fit with a finding from earlier this year that healthy habits like not smoking are more important to living a longer life than being thin is. One law professor was so sure that longevity would continue to improve that he offered to bet an activist $10,000 that life expectancies would continue to rise.

No wonder that Brownell and Ludwig wrote that “society does not have the luxury to await scientific certainty” before adopting their preferred heavy-handed obesity policies. Just like with menu calorie labeling—which more evidence shows to be ineffective at reducing obesity—the scientific certainty is often not on their side.