This article is from the Naturism FAQ, by Dennis Kirkpatrick firstname.lastname@example.org with numerous contributions by others.
Why did naturists decide that nudity is worth speaking up for? There
are several appealing things about it:
3.1. Comfort and Health
Anyone who's spent any amount of time in ill-fitting, uncomfortable
clothing knows how good it feels when it's not being worn. Clothing
is, by nature, something foreign to the body, and its presence is
always known to the wearer. When you're not constantly being reminded
that you're dressed, it's easier to think about other things! There is
a tremendous feeling of freedom when nude. Once you have been swimming
nude, you'll never understand why anyone would ever want to wear
clothes in the water.
Medical research has shown that clothing can be unhealthy in certain
situations. For example, evidence supports a hypothesis that wet,
clingy swimsuits can constrict the flow of bodily fluids. Eliminate
the swimsuit, and you've eliminated that problem! Anecdotal evidence
suggests that disease-carrying insects like to hide under clothing -
another potential advantage for the naturist.