Shrek, it sounds like you are just looking for an excuse not to exercise – the Gemara (and many other reliable sources, unlike Oz Vehadar “Lebusha”) make it very clear that a woman has to make herself attractive to her husband. Granted, each man has a different idea of what’s attractive, and if you/your husband has a thing for 300lb behemoths, good for you. Sarah Imeinu was blatantly beautiful completely naturally, so she didn’t need to play tennis c’v. The rest of us would like our wife to be in decent shape – I’m not saying a size 2 is necessary, although it certainly is nice ;)- but at the very least she should be in shape.
The same goes for the so called “untznius” dancing. If the girl is not doing it in front of any men, not including her husband, there is nothing wrong with it. Where is there a halacha against a girl having a nice body, if she uses it only to please her husband? Please find it for me, I would love to see it.