But How Would We Put It in a Pill and Advertise It on Television?

Here's a squib from the Chicago Tribune about a study I didn't see anywhere else:

Even moderate exercise can dramatically prolong a man's life, new research on middle-age and elderly American veterans reveals. The Department of Veterans Affairs analysis found that brisk walking 30 minutes a day at least four to six days a week was enough to halve the risk of premature death from all causes. That conclusion applies more or less equally to white and black men, regardless of history of cardiovascular disease.

Anybody have the reference for the original study?