Let me tell you folks, senior diets suck. By the time a dog gets to be 7 years old, vets start pushing you to put them on lower calorie and low protein diets. Unless your dog has serious health problems, don't fall for it.
You will end up starving your dog, as he loses weight and muscle mass. It's tough to slowly help them gain back the weight they lost.
Dogs need protein, there's no way around it.
I am now adding cooked beef to his prescription diet, as it was slowly starving him....it looks like we caught it in time.