Hi - I'm new. I just found out that one of my 14-year-old cats has a food sensitivity. I've always fed them the same good stuff with no problems - I started on Science Diet when they were kittens, then switched to Eukanuba when it came available, then switched to Science Diet Senior Hairball Formula when that became available.
My vet told me cats can develop a sensitivity to a food at any time, and it's very common, especially in older kitties (past 7 years old). My Boo had a slightly elevated liver enzyme, which, my vet said, could indicate Inflammatory Bowel Disease. Luckily, it can be remedied by changing his diet. So I'm switching to Waltham's Selected Protein Duck and Rice Formula, a prescription-type cat food that only vets sell. I'm hoping he'll stop throwing up (he didn't do it all that often, but more lately than he ever has in is 14-year life so far), and I'm hoping he'll regain some of his energy and weight.
The moral of my story is that I'm so glad I took my kids in to have complete physicals with blood work and urinalysis, because now I can nip this problem in the bud and hopefully he'll live many more happy years.