Plateau question

tammyclair

I swim 5 days a week for an hour. My pace is moderate – about 66 lengths in an hour. I swim the front crawl. I love to swim. I really hate other exercises – especially the treadmill and elliptical machine. I just don’t want to cross train. I just want to swim. However, I have stopped loosing weight. I was loosing a 1lb a week until November. I am 5’4 / 204 lbs. I have been doing this since June of 2011. I rarely eat my exercise calories. Can anyone help me understand why this plateau is happening?