Your vet is going to provide you with the best solution to transitioning your dog off of hotdogs and onto dog appropriate food, and you'll probably be more inclined to stick to it after discussing it with a professional.
I've been trying to get her to lose weight, but she acts so sad.
It sucks to feel that our pets are sad, I know, but you have to do what's best for them.
My dog was diagnosed with pancreatitis about a month ago. He was vomiting daily, usually with blood in the mix. He could no longer eat anything other than his low-fat prescription food.
It was a transition for us as well. He didn't eat human food on a regular basis, but I'd often feed him crusts off of my pizza, or allow him to have a small scoop of peanut butter when he took his medication for seizures. Once he was diagnosed, he could no longer eat any of those things. He would still come and sit by me and wait for me to give him small table scraps. Within a few weeks, he had moved on and now just lays down next to me instead of giving me his starving dog eyes while I eat.
You need to be the pack leader. You need to set the tone. Do not be sad for your dog, because you'll be giving her a healthier, longer life to enjoy things other than just hot dogs. Your dog will transition and will also be happy if you are happy.