So I'm force feeding an anorexic cat again and thought I'd share in case anyone else ever finds themselves in a similar situation.
Cat's livers do not metabolize fat very well. So if a cat stops eating for whatever reason and the body sends the fat cells to the liver for processing in order to get energy, the liver fails and the cat will die.
The first time this happened, we didn't know what was up and, after noticing that the cat was losing weight, took her to the vet. They said she was dehydrated, put her on a drip, kept her until we'd spent $600 then just shrugged. So we took her home to die. Then I decided to look into the disease and even though the internet was in its infancy, I found that all I had to do was keep the cat alive long enough for her appetite to kick back in. I was really pissed off at the vet for not telling us that. We have a new vet now.
First, see your vet. Once you know that the weight loss is due to fatty liver and not a symptom of some other disease, it's not difficult to keep the cat alive. If the cat can be tempted at all, add a bit of chicken broth to their water, drizzle a wee bit of tuna juice over their food, warm the food to body temperature to make the aromas more appetizing to the cat. If not, force feeding is needed.
So, I make a slurry of a soft cat food(I'm using Lick Your Chops Chicken and Brown Rice Dinner at the moment), some baby food(Beech Nut chicken and broth because it doesn't have salt unlike that other brand-make sure the food does not contain onions) and some low sodium chicken broth(real not cubes obviously!) or water. Warm to body temperature, stir and gently dribble in the side of the cat's mouth using a syringe. Near the beginning of this process, I add a bit of milk thistle tincture as well to improve liver function. The cat will have to be wrapped in a towel like a mummy, will struggle like mad and will have to be re-wrapped several times during a feeding. It's a victory if I can get 20ccs of slurry down the cat in a sitting and extreme patience is required. The food has to go in the side of the mouth and very slowly so the cat does not breathe it in or choke. It's messy, it needs to be done several times a day and it's going to be several weeks before she starts eating again. I'm hauling her ass into the vet every other day to borrow their scale to keep tabs on her weight.