Being healthy is the part of wisdom as the bible is a book of wisdom. We should always take good care of our body as christians. As we take care of our spiritual life by listening to admonitions and teachings of Christ, we ought to take care of our physical body by eating good food and exercising.
The knowledge of people about health deteriorating is not true, the health of a person can prosper even as the souls of christians do prosper by hearing the teachings of Christ. The book of Deuteronomy 34:7 reminds us that it is possible for us to stay in good health until death as Moses lived a hundred and twenty years and his eyes were not dim.
So as christians, we should take care of our body, because the bible teaches us to be prosperous and healthy in soul and body. We should abstain from anything that we deteriorate our body like smoking, taking hard drugs and other things that's not good for the body system.
God bless you all 🙏.