One woman with multiple sclerosis has virtually arrested the disease for nineteen years. Well, I think we have to say that having a healthy relationship with God is good for our health. Keeping God's commandments, attending Holy Mass, praying, etc. should be part of any daily health program. This even includes mental health. I have heard it said that when Catholics were more regular in the Sacrament of Confession they were, by percentage, the lowest group to be found in mental institutions.
Poor fitness can lead to poor prayer and a flabby spirituality.
Do these things and you will be fit on earth as well as fit in Heaven.