ROCHTREV asks: "My cat is 12 or 13 years old. He was fine and healthy with no noticeable problems just a few weeks ago. Then my family went on vacation for 4 days (our neighbors gave him food and water while we were gone). When we came home after our 4 day vacation, our cat was noticeably thinner with a very prominent backbone. He still acts normally, but he feels a looks distinctly different. Is it normal for such a big change to set in so quickly?"