The eating non-stop and not gaining can be related to the IBD. Most likely he isn't absorbing all of the nutrients from the food. Has he ever had a full GI panel run through Texas A&M (TAMU)?
He did have blood tested but I don't know if it went through Texas A&M.
Usually B12 is supplemented to kitties that have B12 deficiencies, which are common with IBD (although TAMU has discovered that the B12 deficiencies are more common in IBD kitties with diarrhea rather than IBD kitties with vomiting as their main symptom). B12 deficiency can also contribute to symptoms and the actual manifestation of IBD itself. Why one cat develops this problem over another, who knows....probably at least partially genetic, perhaps some environmental.
I was told he was deficient and needed b-12 at least a year ago.
The TAMU protocol calls for monthly dosing (once the initial dosing tier has been passed through), but many IBD kitty beans do give B12 more often than that. I usually aim for once every 2 weeks to a month now, but I did used to give it weekly when Sasha was at her worst.
I did this too. We started with much more and more often - but I don't remembetr r the exact timing and dosing. Now I give it to him once a month. He pikes maybe once a week which I don't consider a problem. At his worst it was constant. His poop seems ok.
Have you read the TAMU info on cobalamin?
TAMU COBALAMIN THERAPY
No, I hadn't read this but it sounds as if Boomer should be re-checked at his next apt to see if it's better/needs more than once a month of B-12.
The Budesonide has been a godsend for us - her symptoms (daily vomiting despite constant antiemetics, some loose/mucous stool - this went on for about 1.5 years) have resolved completely. She has not had any symptoms for about 3 months (knock wood, antijinx).
Same with me; bude has been great. he did fine on pred too, but I think that's what's caused the diabetis.
Sasha only really gained weight I believe because she developed hypothyroidism after her I-131 treatment for her hyperthyroidism. Because her thyroid stopped working normally, she put 1.5 lbs on and it has been a struggle to get them off. But I'd rather have her be a little heavy rather than a little skinny at her age, so I'm okay with it. ;-)