It is never too late to start a diet and exercise program and for older dogs, you will be doing them a huge favour by ensuring that their achy old bones are not being forced to carry unnecessary blubber. I currently own 5 border collies Sven Kums Belgium Jersey , with the smallest bitch weighing 18 kilos and the large male weighing 23 kilos. A slim and trim Labrador would not be very much taller than my male but may be a little heavier , maybe around 28 kilograms. To obtain any benefit from putting your dog on a diet, you need to be totally committed to the program, as must the rest of the family, your neighbours and friends. No point in having a diet if the dog is getting treats and tit bits from everywhere else. There can be no between meal treats and the feeding of scraps from the dinner table must be stopped. Any other pet food, such as the cats food, should be put out of reach. Do not leave any excess dog food lying around for him to eat later. Human food must not be left where the dog can reach it and refuse bins must be secured. It does not matter what type of food you currently use to feed your dog. As long as you start to give the dog less with immediate effect. You must reduce the amount of food being fed to the dog by at least half. For my dogs Steven Defour Belgium Jersey , around 1 to 2 cups of a high quality, premium brand, dry kibble, mixed with half a cup of water, is all they get in a day. I vary the amount fed to them as their weight fluctuates around their ideal weight. Less food if the weight is going up, more if it has come down.