Doesn't your dog eat? He's in good health, your vet ruled out any disease? He's adult? Therefore, it could be due to a behavioural problem that has to be improved as soon as possible.
A dog that doesn't eat in a regular way pushes his master to often change his food and to try to tempt him with thousand tidbits. This makes it come that the dog often would be overweight or very thin, that he would have gastrointestinal disorders...without omit the stress of those who have to take care of him and, maybe, to spoon-feed him. These behaviours have to be improved because the dog might want not to eat due to health problems, and we'd not realize that in a short time. But, how to do this?
The bowl has to be kept available just for maximium 10-15 minutes.
The type of food hasn't to be changed unless the dog has eaten it with regularity. No extras, no tidbits, no addictions.
Not try to tempt the dog to eat and avoid hitting on him. During his meal, the dog has to be quiet and concentrated. An adult and healthy dog can stay hungry even for 24 hours without any problem and he could also regurgitate a little, that's absolutely NORMAL. Obviously, in case of illness or if it's about a puppy, or a growing dog, or a pregnant/lactating female, the vet has to be promptly consulted!
Di Barera Annalisa - fonte: gruppo facebook “alimentazione a zampe”