America's smoking rate dropped 20% from 1990 to 2005, but the obesity rate rose nearly 50% during the same period. If those trends continue through 2020, the health benefits of the nation's clearer lungs will be offset by damage done by thicker middles, according to a new study. Researchers forecast that life expectancy and quality of life will continue to rise, thanks to medical progress and other factors. But smoking and weight gain both could deprive patients of even longer lives, said a study in the Dec. 3 New England Journal of Medicine ( The continued drop in smoking could improve the life expectancy of a typical 18-year-old by an additional four months by 2020, the study said. But rising obesity rates could mean that theoretical 18-year-old instead will be deprived of an added eight months of life. Researchers based their estimates on nationally representative patient interviews and federal government data. If current trends continue, nearly half of the population will be obese by 2020. About one in five Americans smokes, down from 25% in 1990. If all Americans refrained from smoking and avoided excess weight, life expectancy would increase 3.76 years by 2020, researchers estimated. "Smoking has huge impacts on life expectancy and quality-adjusted life years, but a far smaller proportion of the population can quit smoking," said Allison B. Rosen, MD, MPH, co-author of the study. "That's really the issue." Sedentary lifestyles and cheap, high-calorie food options are making it more difficult for Americans to keep their weight under control, Dr. Rosen said. While high cigarette taxes, smoking bans and marketing restrictions have helped lower the smoking rate, attacking obesity will pose more of a challenge, she said. "You don't have to smoke to live, but you do have to eat to live," said Dr. Rosen, assistant professor of internal medicine at the University of Michigan Medical School. "Cigarette taxes are really the strongest driver of declining smoking rates, but you can't price people out of the market for food." The full and original article can be found here: