I think it's funny when those pilates commercials tell you that you can 'lengthen your muscles' with pilates. This just isn't true. You can't make your muscles longer than they are. If that were so, wouldn't we be taller from pilates? And why would your leg muscles lengthen out if you're mainly working your core? Many of the pilates instructors I know are not long and lean either - unless they have a great diet. In fact, when I was getting certified in pilates, our instructor was a bit on the stocky side. She mentioned that many dancers (especially ballet dancers) are drawn to pilates to correct a lot of the damage that dancing has done to their bodies. This may be why people associate long, lean bodies with pilates. Many of those people are ex-ballerinas. I think you can lean out but this has more to do with diet than anything else.
Carolyn