Instead of going out to eat or hitting a bar with your girlfriends, get physical instead. Go for a run or a hike, go swimming (and hit the hot tub afterward), play racquetball or tennis--the possibilities are endless.
My women friends and I used to go out to eat when we'd go out to get a break from our kids. But the food wasn't great for our figures. We've been doing more active evenings out, and our fitness has increased.