Well, my Garmin says my "fitness age" is 20, (calendar says 65). I think Garmin is saying I have the VO2max of a typical 20 year old. But compared to other avid cyclists, my VO2max is meh. Nowhere near where it was 20 years ago.

Do I look 20? LOL no. But when I'm kitted up with a helmet and sunglasses, maybe, at a quick glance. I weigh the same now as I did at 20.

Do I feel younger than my sedentary friends? Unknown, I don't have any sedentary friends.

But science folk suggest that at the cellular level, active people age more slowly than sedentary people:

"A few years ago scientists at the University of Colorado in Boulder measured the telomeres of young (age 18 to 32) and old (age 55 to 72) subjects. Each age group was divided into two subgroups—sedentary and endurance-trained—creating four groups in all. When the telomeres of old, sedentary subjects were compared with those of the young, sedentary subjects, the oldsters’ were 16 percent shorter. They really were “old.” The telomeres of the old, endurance-trained subjects, however, were only 7 percent shorter than those of the endurance-trained youngsters. That is to say, old athletes had telomeres that were 13 percent longer than those of their sedentary peers. Telomere length was directly related to activity level. Even though science can’t explain why, exercise slows aging by keeping your telomeres young."

Excerpt From Fast After 50, Joe Friel, 2015