My male westie is 8 years old and 26 pounds, what is the best wieght for him?

What is the average weight for an older westie, I believe he is getting a bit lazy, we have cut the portions, but not seeing a substabtial change yet.

Usually westies weigh about 15-22 pounds but of course it depends on his height. He may be a healthy weight. You won't see a substantial loss with just decreasing his intake. Just like humans, they need exercise as well. Take him for walks and cut out treats and/or table scraps. Before putting him on a diet (i.e. diet food) speak with the vet.