The best way I have found to help a dog lose weight is monitor what he's being fed along with exercise. That seems like an easy answer, but once you start paying attention to the food you feed him and how much of it and make changes the easier it is to change the habit. Of course if you change your dog's food, make sure to do it slowly as not to upset his stomach. I have found that purchasing dog food that uses real meat and is a weight loss type food helps. Make sure to follow the amounts listed on the packaging and adjust as necessary. Also, get out there and walk your dog daily. Even if it's just walking for 10 minutes, doing that each day or several times a week will be really good for him and it'll make him happy too!