A new study says life expectancy in the US may decline later this century due to a a sharp rise in obesity nationwide. The research, published in this week's New England Journal of Medicine, says that if obesity levels continue to rise, statisticians may have to shave two to five years from the average American's life expectancy. Such a sustained downward shift in projected life expectancy would be the first such drop in over 200 years.

Forecasting life expectancy by extrapolating from the past is like forecasting the weather on the basis of its history,  wrote the authors of the study. Looking out the window, we see a threatening storm  obesity that will, if unchecked, have a negative effect on life expectancy.  We'll talk with one of the authors about the work, and about what can be done to get the nation to slim down.

We'll also take a look at a new study examining the effects of Vitamin E supplements. The use of Vitamin E and other anti-oxidants has been suggested as a way to help the body fight off cancer. However, new research published this week in the Journal of the American Medical Association suggests that taking Vitamin E could do more harm than good in some cases. Following a multi-year randomized, placebo-controlled study, heart researchers concluded that "in patients with vascular disease or diabetes mellitus, long-term vitamin E supplementation does not prevent cancer or major cardiovascular events and may increase the risk for heart failure." We'll talk about the findings.

Finally, we'll check in with scientists studying Mars from afar. While the Mars rovers have been busy on the surface of the red planet, scientists studying the output of probes orbiting Mars have been making impressive discoveries as well. We'll hear about some of their latest observations, including the theory that, near the Martian equator, a frozen sea of water may lie just a few feet below the planet's surface. The idea could have important implications for researchers looking for signs of life on Mars. Call in with your questions and comments at 1-800-989-8255 (2-3 Eastern). Teachers, find more information about using Science Friday as a classroom resource in the Kids' Connection.

Guests:
Greg Brown
Professor of Medicine
University of Washington School of Medicine
Attending Physician
University of Washington Medical Center
Seattle, Washington

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S. Jay Olshansky
Professor, Epidemiology & Biostatistics
School of Public Health
University of Illinois at Chicago
Chicago, Illinois

David Ludwig
Director, Obesity Program
Children's Hospital Boston
Associate Professor of Pediatrics
Harvard Medical School
Boston, Massachusetts

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James Head
Professor, Geological Sciences
Brown University
Providence, Rhode Island

Books/Articles Discussed:

Olshansky SJ, Passaro DJ, Hershow RC, Layden J, Carnes BA, Brody J, Hayflick L, Butler RN, Allison DB, and Ludwig DS, A Potential Decline in Life Expectancy in the United States in the 21st Century,  New England Journal of Medicine, 352:11, pp. 1138-1145.

"Effects of Long-term Vitamin E Supplementation on Cardiovascular Events and Cancer: A Randomized Controlled Trial," by The HOPE and HOPE-TOO Trial Investigators. JAMA. 2005;293:1338-1347.

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This segment produced by Karin Vergoth