Weight loss in middle-aged cat, periodic vomiting and normal bloodwork

Hi, everybody I have a 8.5 year old kitty who hasn't been feeling well and wanted some... advice? ...recipes? I think I'd welcome just about anything that helps Mack and I out. Up until about four months ago, he'd always been very healthy. Ideal weight is just under 13 pounds, and for about 3-4 years he's been holding steady right around 13. Infrequent hairballs, and he's never been the type to eat non-food items.

Around three months ago I noticed an increase in the frequency of vomit (no hair noted) and switched him to 100% canned grain-free. He usually eats dry grain-free. No improvement, but he really likes canned so I kept him on the exact same formula hoping his stomach would settle down and I could switch back in a month or so. The frequency of vomiting increased to every 3-4 days and I noticed his appetite drop with him eating very little for 24 hours after being sick. At this point I noticed weight loss and scheduled an exam the following week at his regular vet.

His exam was normal: Dental plaque, but likely not causative. Negative fecal. Heart rate normal, no murmurs. However, he weighed only 11.7 pounds. We agreed on bloodwork. Differential at the time was diabetes, hyperthyroid, kidney/renal disease, or inflammatory bowel disease (IBD). Bloodwork came back with all normal values, so by default we agreed to treat for IBD. Mack received a glucocorticoid injection and I switched him to a novel protein (Natural Balance Duck/Pea). He wasn't interested in the canned, so we just did the dry -which he seemed to like. For the next three weeks he did well. The injection only lasts for 10 days, but he continued eating and I could see weight gain (vomited once). We went back for the recheck. He weighed 12.1 pounds, was maintaining on diet alone, so the vet and I agreed to hold off on further medications.

This brings us to now. Mack has been vomiting on average every 14 days, but getting over the nausea within a few hours. He vomited again last week and his appetite is sporadic again. Sometimes he'll eat the dry fine, sometimes only with his freeze-dried duck treats crumbled into, sometimes not even the treats themselves. Last night he acted like his mouth hurt, took the treat gummed it and spit it back out. I crumbled it and he grudging ate it. This morning I crumbled a few more and he ate happily. This past hour he's been picking at the dry.

I might catch flack for this, but I'm not adverse to the idea of low-dose maintenance glucocorticoids. If there a very good reason otherwise, please educate me. I'd prefer to use diet alone, but where to start? What brand? Raw or freeze-dried? Should I consider something other than duck knowing he may have IBD? I would consider homemade cat food but the risk of imbalanced vitamin/mineral levels makes me nervous.

You won't catch flack from me, my kitty has been on a steroid for 4 years to control IBD.  It's better if it can be controlled with diet alone but that isn't always possible.

Some people swear by raw for their IBD kitties, I hadn't tried it.  Have you tried some of the foods that are almost exclusively meat, liver, and supplements.  Foods like Nature's Variety LTD, Hounds and Gatos, Wild Calling.  Your kitty might be interested in eating the wet of those brands.  Without getting into the wet versus dry debate, I believe that wet is more easily digested.  I would try introducing other novel proteins one at a time.  Kitties can become sensitive to a protein when they are fed that protein exclusively.  I know the three that I mentioned have foods in some unusual proteins like pheasant, pork, and rabbit.

One of the reasons why your cat lost weight when you switched him to canned food *could be* because the canned has less carbs than dry food and is more bioavailable. My cat lost weight as well when I switched from dry to canned (probably about a pound over a few month's period). 

I was in your shoes last March. My vet was very close to diagnosing my cat with IBD, although my cat was not vomiting but was having loose, mucous-y stools out of the blue. I have 2 suggestions for you that have completely helped my cat:

1.) Consider adding a probiotic to his diet. I use 1/2 a capsule of Nexabiotic once a day (in his evening meal). I tried using the "Natural Factors Acidophilus Bifidus Double Strength" probiotic first because many people on this forum recommend it but that did not get rid of my cats diarrhea. 

2.) Since you are open to the idea of a freeze-dried raw food diet, I would absolutely recommend you give it a shot. I have my cat on a homemade raw diet but there is nothing wrong with freeze-dried raw. Stella and Chewy's is an excellent brand of freeze-dried raw and they have a Duck-Duck-Goose kind that you can try. If you do go the free-dried route, I would suggest that you add water to it to make it the consistency of canned food.

I don't know if my suggestions will help your cat and your situation, I only mean to share what helped with my cat and share my experience in case it helps others.

Hope that helps!!