The New Jared?

I've been on a pseudo-subway diet for a while now. I eat subway's fresh value meal for lunch everyday, and I walk a TON getting to and from work and school. I've lost 25 lbs so far, and I think I'm looking pretty good. The only problem is, I feel like I'm losing physical strength as a result. Does such a regiment cause muscle m loss? How would I counter-act it? I wanna look better, but I don't wanna be a skinny b*tch.