In my case I don’t react well to sun exposure. If I have a short sun exposure I will feel the nerves in the areas where I usually lose muscle (tingling, pain, skin problems). If I stay for a long time, I can even have some muscle loss in that areas.
It happens the same (but way worse) when I masturbate. If I don’t reach orgasm I can later just feel the nerves. But if I orgasm, I will later experience some muscle loss and fat gain in the areas where I feel the nerves.
Also, as others have also mentioned my skin doesn’t get tanned in the sun.