Bodily exercise is profitable, but spiritual exercise is beneficial above all.
I buffet my body and make it my slave, so that I who preach to others am not disqualified.
Both of those statements came from St. Paul the Apostle. He is talking about the primacy of spiritual discipline over physical FITNESS, but also about the subjugation of the physical body because lusts and passions run wild no matter what "shape" one is in.
Yes, keeping healthy is important. Again, St. Paul: No man ever hated his body, but nourishes and cares for it.
However, "healthy" by necessary standards and "healthy" by today's humanistic fitness-obsessed standards are two TOTALLY different things.
Exercise of the body OUTSIDE of the context of exercise of the soul is vain, useless and ultimately will lead one to care more about their physical life than their soul.
Exercise of the flesh should ALWAYS be as part of disciplining and mortifying the flesh so it is under your control as you obey Almighty God.
Otherwise, it's like encouraging an unbroken horse to run... no matter how often you feed him and then let him run around, he will never be controllable. He has to be broken and brought under your command first.
A rightly-trained horse was once more important to a gentleman, soldier or knight than even a weapon, and all the other Catholic attitudes are like weapons we can never wield rightly if our "horse" (our flesh) is wild and unmanageable.
Ask St. John Vianney, St. Francis of Assisi or hundreds of other saints where bodily fitness ranked in the grand scheme of things.
Francis called his body "Brother Ass", and like any other pack animal, it needed a swat on its namesake hind-parts in order to act obediently.
Our bodies are no more, and no less, the instruments of righteousness or sin than what we MAKE them to be under Christ, or ALLOW them to become under Satan. There's no middle ground.
St. John Vianney, pray for us.
Immaculate Heart of Mary, triumph soon!
Most Sacred Heart of Jesus, have mercy on us.