The Economist says Chronic stress really does cause you to age faster, (and new word watch bonus)
because your telomeres get shorter:

Body cells have age limits. They have caps called telomeres on the ends of their chromosomes, and these caps shorten after each cell division. Eventually, the telomeres become too short for division to occur again. When this happens the cell dies. This “limit to life” was first discovered in the 1960s by Leonard Hayflick, at the Wistar Institute in Philadelphia, and it has become known as the Hayflick limit.

The obese also suffer from premature shortening of the telomeres. So far there's no treatment of this condition.

Until then, there's always yoga class. ooooohhhmmmmm.

Bonus: New word watch: telomeres.