The New England Journal of Medicine study released Wednesday looked at previous health trends culled from national health surveys to forecast life expectancy and quality of life for a typical 18-year-old from 2005 through 2020. Past declines in smoking over the last 15 years would give that 18-year-old an increased life expectancy of 0.31 years. However, growing body mass index rates would also mean that the teenager would have a reduced life expectancy of 1.02 years, giving a net life expectancy reduction of 0.71 years. Researchers from Harvard University, the University of Michigan and the National Bureau of Economic Research point out that though life expectancy will increase in the future due to factors such as overall health care improvements, better nutrition and education, rising obesity rates may eventually slow that progression. 'This is a bit of a wake-up call,' says Dr. Allison Rosen, assistant professor of internal medicine and health management policy at the University of Michigan and co-author of the study. '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. I wasn't sure what to expect from the results. Part of me thought obesity would be the driving factor, but I was surprised by the extent of our findings.' When it comes to life expectancy, some would rather have cheesecake now than an extra few months of life down the road. Rosen says people should think more in the short-term: 'I've had patients lose weight and stop smoking, and the changes in their quality of life can be dramatic. One patient lost 55 pounds, and before that he was in a wheelchair half the time. I know smokers who like to go run around with their friends, but they get short of breath and tired rapidly. Life expectancy may not come until years later, but you can experience quality of life right now.' 