Try a "lite" dog food, such as Nutro.

I have a lab/chow mix that was up to 60 pounds. The vet thought she should be at least 10 pounds lighter. So I switched her to Nutro Lite, measured her dinner (2 level cups a day) and added a few green beans. It took a year, but she's now down to 52 pounds. The only treats she gets are one small, inch and a half biscuit in the morning and one snausage at night. I tried carrots, but she won't touch hem.

Just remember that your dog didn't get 'fat' overight and it'll take a while to safely get the extra weight off.