My four year old cat has been doing well on her new limited ingredient food for the past couple of months, as well as the grain-free version of the same brand that I have been feeding for about the the past week. There has been absolutely no vomiting on this new food, like she had been doing on all of her previous foods. She also likes the new food and has a good appetite. However, I have noticed that she has begun losing weight. She is not emaciated or anything--just smaller than she was. In truth, she was starting to get a little chunky, so losing weight may not be a bad thing, but it is a little troubling that it seemed to happen for no reason. The new food does have totally different ingredients than the other foods, but the fat content is about the same (12% versus 10%). The new food does not have any corn, wheat, soy, or rice (or any other grains), but those foods are not fattening so I can't see why eliminating them would have made her lose so much weight. Could it be a medical issue instead of a diet issue? I wonder if I should have her checked out by the vet.