Half of babies born since 2000 may live to 100 years old. Another study says life expectancy will be cut short due to obesity. Which is it?

Living to 100 may be seen as a long life now, but according to a new review, it may be the norm for babies born today. The article, appearing in the medical journal The Lancet, shows that based on current trajectories, more than half of all babies born in industrialized nations since the year 2000 can expect to live into the triple digits. The trends included in the article show that many Western nations will have most people living past 100, with half of all babies born in 2007 in the U.S. likely to live to age 104.

"I guess it's good news for individuals and a challenge for societies," said Dr. Kaare Christensen, an epidemiologist with the Danish Aging Research Center at the University of Southern Denmark, the study's lead author. "If this trajectory continues, half the babies will be 100 and I think that gives us a new perspective for how to plan your life, basically," he said. Christensen said that while the progress in life span during the first part of the 20th century came by reducing infant mortality, increases in longevity since then have come from improving life at older ages, and that will need to persist for the projection to hold up.

"If we want to have a continuing increase in life expectancy, the progress has to occur at older ages," he said. Christensen said that the aging population will also likely be a more vibrant population, with a higher quality of life than people of that age now. "The good news is people will generally be functioning well -- it's more like they're postponing their aging process," he said.

Some researchers backed the new report's hypothesis.