A cat who doesn't eat for any reason is in danger of getting hepatic lipidosis (fatty liver disease).
You did not give a lot of information about your cat, but, bad breath, weight loss and decreased appetite could be from kidney disease, or a problem with the GI (gastrointestinal system). It could also be something simple such as dental disease (too painful to eat) or an upper respiratory infection (a cat won't eat if he can't smell his food), Your vet will be able to sort it out with diagnostic's.
This site complies with the HONcode standard for trustworthy health information.
The Content on this Site is presented in a summary fashion, and is intended to be used for educational and entertainment purposes only. It is not intended to be and should not be interpreted as medical advice or a diagnosis of any health or fitness problem, condition or disease; or a recommendation for a specific test, doctor, care provider, procedure, treatment plan, product, or course of action. Med Help International, Inc. is not a medical or healthcare provider and your use of this Site does not create a doctor / patient relationship. We disclaim all responsibility for the professional qualifications and licensing of, and services provided by, any physician or other health providers posting on or otherwise referred to on this Site and/or any Third Party Site. Never disregard the medical advice of your physician or health professional, or delay in seeking such advice, because of something you read on this Site. We offer this Site AS IS and without any warranties. By using this Site you agree to the following Terms and Conditions. If you think you may have a medical emergency, call your physician or 911 immediately.