My dad is in his late 50s and only started cycling about 3 years ago.
And he has raced in the amateur old guys state championship crits, and not embarrassed himself.
In the first Hotter n Hell 100 he did, he road off at the 70 mile mark and my friend and I, in furious pursuit and working together (friend does triathlons) couldn't catch him.
And my dad has a gut as well.
Point is, fitness isn't so much about age, esp. in cycling.