Increasing Obesity Rate Eliminates Benefits from Smoking Cessation

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Declines in smoking over the past 15 years have increased life expectancy for Americans, but the rise in obesity has eliminated that positive trend, according to a new study this week by the New England Journal of Medicine.

Researchers reviewed previous national health surveys to forecast life expectancy and quality of life for a typical 18-year-old from 2005 through 2020. A non-smoking adult has an expected increase to life expectancy of about 0.31 years. However, should that same adult become obese, life expectancy would drop by 1.02 years, a net reduction of almost three-fourths of a year.

Smoking is still the leading cause of preventable death in the United States, accounting for about 18% of deaths each year. Obesity currently accounts for up to 15% of deaths. If all American adults stopped smoking and achieved a normal weight by 2020, researchers estimate that their life expectancy would increase by nearly four years.

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The researchers from Harvard University, the University of Michigan, and the National Bureau of Economic Research looked at date from the National Health Interview Survey, the National Health and Nutrition Examination Survey (NHANES), and the Medical Expenditure Panel Survey from the 1970’s through 2006. Past trends on smoking and BMI were cross-matched into 16 groups and relative risks for death were approximated. The study did not examine variations by race or ethnicity.

As a population, Americans are smoking less. Today, about 1 in 5 Americans smoke, compared to 2 in 5 in the 1970’s – a decrease of 20%. However, according to statistics from the Centers for Disease Prevention and Control, 34% of US Adults are obese (BMI greater than 30), which has more than doubled over the same time frame. The World Health Organization has estimated that if the current trend continues, 50% of US adults will be obese.

The authors point out that overall life expectancy is still likely to improve over the next decade, because lifespan is improving in other areas of health care.

"This is a bit of a wake-up call," says Dr. Allison Rosen, study co-author and assistant professor at the University of Michigan. "We have always attributed so many of our health problems to smoking, and this emphasizes that we're getting health improvements from declines in smoking. But changes in the rates of obesity are starting to outweigh the declines in smoking.”

What is needed, according to the study authors, is a change in obesity policy and the environment, just as there was with smoking. Improvements to health care, better nutrition and education may slow the progression of obesity and extend life expectancy.

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