Do Be Careful. Aging may be ''normal'', but look at all the pressure to be that ideal. It will cure your every woe; yes? No, not really. There actually is/are reward(s) for fitness. Beyond the loooong term help in your heart, lung, brains, vessels, muscle tone, a hormone is released that gives a delightful sense--period. And a little grace is attractive & never hurt anyone.
HRT and fitness. Men at middle age should consult the doc about hrt, in the form of testosterone, "t." which has many good effects: prevents osteoporosis (like "e" does for women!), muscle mass, libido, mood and mental energy. The best fitness effects result when your doctor monitors the whole range of hormones, including estrogen, to prevent the t supplementation from getting transformed into obesogenic estrogens.