How old are you? How old is your body? The answers to these questions should be the same, but a great many factors can contribute to a noticeable disparity. Women's Health magazine points to the significant role fitness level plays in determining your body's age.

In terms of genetics, people who exercise regularly are 10 years younger than inactive people of the same chronological age. Researchers from King's College in London found that in twins, those who exercised had the longest telomeres -- genetic markers that shorten with age, oxidative stress, and inflammation. And, because exercise has been linked to a reduction in stress and inflammation, researchers posit that it therefore affects telomere length.

For other methods of finding out your "Real Age," visit (where else?) RealAge.com and complete their online physical assessment.