Know ye not that your body is a temple?
This is a verse that has always stood out to me. I think it is very important that we take care of our bodies[temple]. There are two things that I believe need to be addressed. First, appearance and second physical state/health. There is some linkage between the two of course.
So what is Vanity?
1. excessive pride in or admiration of one's own appearance or achievements:
2. the quality of being worthless or futile:
Which definition applies? I would argue that excessive pride, while it can be categorized as pride, is also worthless/futile, meaningless. The book of Ecclesiastes users the word 'vanity' and 'meaningless' a lot. I think when approaching this topic, it is a good idea to take a look at Ecclesiastes. Solomon, explored everything the world had to offer, science, wisdom(he was already the wisest...??) and philosophy, materialism, morals, and everything else "under the sun". While you should definitely read it yourself, The gist of it, is that the only true meaning, the only point, is God. Or as the pencil with an eraser on each end that my grandma gave me said "Life without Jesus is like this pencil, no point to it."
On the matter of appearance, Is there something wrong with dressing up, or caring about your appearance? No, I don't believe so. I think it is important to dress cleanly. I don't not believe caring about style is a bad thing either. The issue is when our focus turns away from Jesus and instead is centered on ourselves and what other people think of us. We should find our identity in Christ.
On the matter of physical health, I believe it is very important that we take care of our bodies. There is the concept of our body being a temple. That alone should be enough encouragement to take care of it. Beyond that, think about some of the things that we are commanded to do in the bible, and consider whether those can be accomplished if we let ourselves turn into couch potatoes, slugging around eating unhealthily.. Yeah, That doesn't seem to fit in my mind.
For myself, I also think about what a hero is. I heard someone once describe a hero as the following: Someone who is in the right place, at the right time, is prepared to take action, and chooses to take action. If I am ever to be put in the position where I would need/be able to choose to take action, I certainly want to be prepared. That being said, the same thing I said about appearance applies here. Our focus should be on Jesus, and growing closer to him. At the point where taking care/improving our physical body interferes with that, it is an issue.
“For bodily exercise profiteth little: but godliness is profitable unto all things, having promise of the life that now is, and of that which is to come.” - 1 Timothy 4:8