He's compiled a list of 100 health-related factors, among them tobacco and alcohol use, diet, prescription and over-the-counter drug use, your parents' health, even pet ownership and the highest educational level completed by your spouse, and worked all these into a quiz to determine your "real age."

If you've taken your health for granted, be prepared for a shock.

He then explains how to follow a personalized age-reduction plan using a range of methods, from quick fixes (use a helmet while bicycling), to moderately easy changes (avoid sun and radon exposure), all the way to the most difficult changes (reduce the stress in your life).

Emotional issues are given as much attention as physical ones; Roizen says, for example, that seeing a psychologist to help work through serious personal problems can reduce your chronological age by 8 to 16 years alone.

RealAge may appeal to Fountain of Youth seekers, but will be especially useful for folks who are out of shape and too overwhelmed to start a fitness plan, and for those who are understandably confused by the wealth of contradictory health reports in the news.

Dr. Roizen has done an excellent job of organizing and explaining essential health information, from defining health concepts such as blood pressure (and explaining how to lower it) to distilling facts about diet, supplements, and herbs.

Far from faddish, RealAge clearly presents only advice that's been proven effective in clinical trials.