Well, personally, I don't think free feeding will work for weight loss. There's just not enough control over who is eating what.

I feed once a day, at night. The dogs get approximately two cups of food or a 1.5 pounds of raw stuff. Some get a little more or a little less depending on their size and activity level.

Some of my dogs have been starved and have food issues. They can't handle having the volume of their food reduced so when they need to loose a pound or two, I replace half a cup of their kibble with either pumpkin or green beans. Most dogs love either one. They are full of fiber so the dog still thinks they got a full meal. They also get carrots for treats.

If you can't reduce his food or change your feeding schedule, then your option is the same as if you want to loose weight--Move more! He can eat the same amount and loose weight if he gets more exercise. It's just like humans--burn off those calories and loose weight!