To make holy is to set apart, to especially dedicate, to separate. The word holy also makes reference to health, cleanness, and sacred or religious dedication.
External holiness or physical holiness
The external holiness is the visible separation from what is vane and profane. We usually understand that as believers, we should dress and act according to what is pleasant to God.
Probably God may not be too concern of the color and the size of my clothes. But I understand, that my moral conduct should be approved by men to be approved by God. In other words, my moral standards should be higher than those of the world.
The bible says that our bodies are temple of the Holy Spirit. Therefore, I should take good care of it.
Why should allow myself to overeat, when I say that Jesus set me free? If I overeat after being set free by The Lord, it is because I choose to do so. If I know it’s against my body, I should stop.
If I say, I can’t. Then, where is my freedom? The same is with other things that contaminate my body. As a believer, I believe that the Lord is powerful enough to set me free of all contamination of sin. This only happens if I follow his commandments and call to him for help, when I can’t do it by myself.
The bible also says that at the moment a man look at a woman with desire, he is an adulterer. Then, I should not dress to provoke anyone to look at me with lust. So, I will dress to please the Lord rather than to please my flesh or the people.
The time I spend with God in pray and adoration, is part of living a holy life.