Wherever there is life, it is worth a try to make life better. I would suggest you try a few things and let me know what your results are. Give Dia-IonX in food or water. It contains homeopathic remedies that are usually helpful to cats. It may help catalyze the healing process and help better utilize nutrients given. Also give 250-500 mg daily of the amino acid carnitine in divided doses. Cats have a high requirement of it. Your veterinarian may have some or you can get it at a health food store. Also, a dietary supplement made by Standard Process called Thyroid support or Whole Body Support could be helpful; vets or chiropractors can usually get it. You will need to act quickly to get the rate of weight loss to slow down. You might also try to feed some canned food and add a high quality fish oil supplement to it. Be advised not to get any mint flavored oil; cats hate mint. We will look forward to your progress report.