I don’t think there’s anything wrong with wanting to be thin, or thinner than you are. In fact, I’d say there might be something wrong if you were not affected by (or hadn’t internalized) the hordes of media messages we receive on a daily basis, suggesting that this be your ultimate goal. But, it’s interesting to me how body dissatisfaction so easily turns emotional and destructive.
Outside of your weight or shape, I’m sure there are things about your appearance that you don’t find ideal. Maybe your hair’s frizzy, or your complexion’s spotty. Maybe your feet are funny. As a personal example, I point to my fingernails. No matter what I do, they don’t grow. As soon as they’re about an eighth of an inch beyond my fingers, they snag/peel/break, and they’re off. Sure, there are some things I can do (nail hardeners, for example), but the bottom line is, oh, well, I’m never going to have long nails. And I’m ok with that.
Why can’t we be this way about our bodies? Desiring to be thinner, but resigned to how we are. We might be disappointed by a “problem” feature, and we may even try to fix it, but nothing, in my mind, packs the same emotional punch as not weighing what we should. Nothing has such a grip, such a soul-clamp, on who we are as the gap between our bodies and how we want them to be.