I just tried one of the most informative websites I have ever come across and got some good news.
The site is RealAge.com, and it takes visitor through a series of questions about one's vital stats -- age, height, weight, blood pressure, cholesterol, eating habits, exercise habits and so on, and then computes your "RealAge" which is the actual age your body seems to be operating at.
The happy news is that I came out 8 years younger than my calendar age, or in other words I have the body of a 33 year old.
I felt goooood!
It also told me how I could lower the number even further, in some detail, by changing my diet and some of my personal habits (flossing every day, for example.)
Strangely enough, it also told me to exercise less than my usual -- 6 days a week for 1.5 hours -- because studies showed that to much exercise is not good for me... I plan to ignore that advice.
I recommend the site heartily -- it is the first I have ever seen that is so comprehensive and immediately useful on the topic of one's health and habits.