Hi I was just about to put my cat down after a year of him being sick after every meal, rubbling tummy and looking in pain, he also lost weight you could feel his spine. I had all the treatment at the vets endoscope both ends, all they found was an inflamed stomach. They advised their own vet food or chicken rice and fish, all to which never change his condition. Today he is looking 100% better and his started fighting with other cats again. I only feed him turkey breast and fat free beef all cooked in plain water or lightly fried, his put on weight coat looks healthy, I did give him fish but he was ill again. It can be expensive and time consuming I use slow cooked beef and chop in up small, freeze it in small portion the turkey is sainsburys basic £2.00 and do the same with that You will find that they feel more satified. occasionally I give then raw chicken, the vet said no, but they dont cook the mouse before eating it and they go crazy for raw meat.
Julie