The National Research Council (NRC) recently issued a report suggesting that past smoking and current obesity levels are major reasons why U.S. life expectancy at age 50, though still rising, has not kept pace with that of other high-income countries, such as Japan and Australia.

Sponsored by the National Institute on Aging’s Division of Behavioral and Social Research, the report explained that the health consequences of smoking, which 30 to 50 years ago was “much more widespread in the U.S. than in Europe or Japan,” continue to influence today’s mortality rates. It anticipated, however, that “life expectancy for men in the U.S. is likely to improve relatively rapidly in coming decades because of reductions in smoking in the last 20 years,” while women’s mortality rates “are apt to remain slow for the next decade.”

The report also concluded that current obesity rates “may account for a fifth to a third of the shortfall in longevity in the U.S. compared to other nations,” although “no clear-cut marker exists for obesity, physical inactivity, social integration, or other risks.” Nevertheless, NRC has warned that “if the obesity trend in the U.S. continues, it may offset the longevity improvements expected from reductions in smoking.” The agency has thus urged the continuation of studies “that take advantage of natural experiments, such as increased cigarette taxes or a dramatic change in the use of hormone therapy,” to complement randomized controlled trials. See The National Academies News Release, January 25, 2011.