Of course Boo would behave at the vets....he is very worldly now, and a trip to the white coats shouldn't phase him....as to weight...I am thinking the vet must have had a reason to say that. Boo must be a little kitty?? Did the vet caution you against any sort of rapid weight loss? Kitties develop fatty liver disease, which is life threatening, with quick weight loss. I would begin by switching him to 'lite' food, the same amount you feed him now, and slowly slowly decreasing it. Two pounds seems like a lot of weight loss for a kitty that weighs in at 10. None of mine have been intimate with the number 10 for quite some time, save for Tex.