our 4 year old black lab "big boy buster" needs to lose weight, about 4 kg. He's got arthritis in one of his elbows and is on monthly carthrogen injections and we know excess weight is bad news for him - he's a chunky kind of lab.
He went to the vet for his boosters and check up and despite all our efforts he's still not lost enough weight yet - we've really cut his dried food down and we bulk it up with veg, we give him raw carrots and other veg as treats altho he does have markies and gravy bones - 2 -3 at night. He's on Autarky light mature - we get this as we've a 11 year old lab with a sensitive stomach (who needs to put a bit of weight on) He's an active and playful dog and has three good walks a day.
I would cut out everything else use a couple of bits of kibble from his daily ration as his treat. Are you weighing his food and are you feeding him for the weight of dog you want him to be ( as opposed to the dog he is now).
My Dobermann is very overweight 8kg and we have put her onto Burns high oats and no treats at all she has lost 1kg in 2 weeks but it has been hard listening to her crying for food all the time, but I know it will be worth it in the end, cutout treats all together the vet told me if you have to give treats then take a handful of her daily food allowance and use that as your treats, but they don't need them really they would prefer a play with a toy instead of a food treat I am learning that now.