How do i slim down my legs????

So, my legs have always been a little bit bigger than my long and lanky upper body, but recently I have noticed a change in them. It seems not only have my legs gotten bigger, I have also gotten curvier. I don't really understand why my shape has changed- I have always had a pretty straight build!! I know that some of it is muscle, but I'm thinking that there is some fat under the muscle. How do you get rid of it? And how do I reduce the amount of muscle tone in my legs? I have been doing a lot of cardio/running, etc. but nothing has seemed to slim them down. I think spinning made them bulkier in the 1st place, so i'm laying off on that. Any suggestions??? Also, my diet is basically low carb, high protein- could this be the problem? Should I add in more carbs? I have always lost weight reducing carb intake, but not now!