Dog i just adopted seriously overweight?

so i adopted a 1 and a half yr old female golden retriever today. I have a 8 month old male german shepherd and for the most part they are getting along good. My male is a pest but they've been playing good. So my question is how do you get a dog to lose weight? My german shepherd is perfect. I've had him since he was 9 weeks old, but I just adopted a female golden retriever and she is way over weight. The owners said they didn't have time to walk her or anything so that's why they got rid of her plus she is to big and the lady has some illness and can't handle a big dog. So i take my male out twice a day and walk for 45 min. Or i take him to my dad's farm to let him run. Will that be enough for my golden to lose some weight? She really looks like humpty dumpty.