A Veterinarian’s Perspective
I’ve been a licensed veterinarian for more than a decade, and if there’s one complaint I hear most often from owners of senior cats, it’s this: “She eats like she always has, but she keeps getting thinner.” By the time a cat reaches 17, that observation deserves serious attention. In my experience, weight loss in an older cat who still has a good appetite is rarely “just old age,” even though many people are told that early on.
I want to walk you through how I think about this problem in real clinical settings, based on the cats I’ve actually treated—not theory or textbook lists, but patterns I’ve seen again and again.
What I Notice First in the Exam Room
A 17-year-old cat who is losing weight usually doesn’t look as sick as people expect. They’re often bright-eyed, vocal, and very interested in food. Owners will tell me the cat still runs to the bowl, begs at the counter, or even seems hungrier than before. But when I put my hands on the cat, the changes are apparent.
The muscle loss along the spine and hips is usually the first giveaway. I’ve had owners swear their cat “just looks slimmer,” but when I feel the shoulders and thighs, there’s apparent muscle wasting. That matters because muscle loss points to chronic disease, not simple calorie shortage.
One case that sticks with me involved a 17-year-old indoor cat whose owner thought she needed “better senior food.” The cat was eating well, sometimes more than usual, but her back end was getting bony. Bloodwork showed hyperthyroidism so advanced that her heart rate was nearly double normal. Without testing, that would have been missed until a crisis.
Hyperthyroidism: The Most Common Culprit I See
If I had to pick one diagnosis that explains most cases of weight loss with a strong appetite in elderly cats, it would be hyperthyroidism. I’ve diagnosed it countless times, especially in cats over 15.
These cats burn calories at an alarming rate. They eat, digest, and then essentially waste energy as heat. Owners often notice subtle behavioral changes before the weight loss becomes obvious—restlessness, louder meowing, or sleeping less. Sometimes they describe the coat as greasy or unkempt, even though the cat still grooms.
I once treated a cat who was stealing food from other pets and still dropping weight. The owner assumed the cat was just “being dramatic.” After starting thyroid treatment, the cat gained weight steadily over a few months and became noticeably calmer. That turnaround is something I’ve seen many times, and it’s why I’m firm about testing thyroid levels early rather than waiting.
Kidney Disease Can Look Misleading at First
Chronic kidney disease is another condition I encounter constantly in senior cats, and early on, it can be deceptive. Many cats with kidney disease still eat normally, or even seem extra hungry, while slowly losing weight.
What owners usually mention first isn’t appetite—it’s increased drinking, bigger clumps in the litter box, or mild nausea that shows up as lip smacking or walking away from food and coming back later. The weight loss tends to be gradual, which is why it’s often dismissed.
I remember a cat whose owner thought the weight loss was due to “picky eating.” The cat was still finishing meals, just in smaller bursts. Blood tests showed kidney values well outside normal limits, yet the cat was still energetic. Early dietary changes and fluids significantly improved her comfort and slowed further decline. Waiting would have closed that window.
Diabetes and Why It’s Often Overlooked in Thin Cats
People associate diabetes with overweight cats, but I’ve diagnosed diabetes in thin, elderly cats more times than I can count. In these cases, the cat eats because the body can’t properly use glucose. Despite food intake, tissues are essentially starving.
Owners often report increased hunger, weight loss, and increased urination. Sometimes the coat becomes dull, and hind leg weakness appears later. Because the cat is eating, diabetes isn’t always suspected until bloodwork is done.
One older cat I treated last winter had lost a noticeable amount of weight but still screamed for meals. The owner assumed age-related muscle loss. Insulin therapy stabilized the cat’s weight within weeks, and her strength improved enough that she could jump onto the couch again.
Digestive Disorders and Cancer: Harder Conversations
Not all cases have straightforward fixes. Intestinal disease, including lymphoma or inflammatory bowel disease, can allow a cat to eat but prevent proper nutrient absorption. These cats may have intermittent vomiting or diarrhea, but not always. Sometimes the only sign is weight loss.
These are the cases where experience matters most. I’ve learned to trust my hands during an exam. Thickened intestines, abdominal discomfort, or persistent low-grade anemia raise red flags that food changes alone won’t solve.
I’ve had to tell owners that, despite a cat’s appetite, a severe disease is present. Those conversations are never easy, but early diagnosis still matters. Even palliative treatment can significantly improve comfort and quality of life for months or longer.
Common Mistakes I See Owners Make
One of the most common mistakes is switching foods repeatedly without diagnostics. I understand the instinct—food feels like something you can control—but I’ve seen cats lose valuable time while owners chase “the right formula.”
Another mistake is assuming a good appetite means a problem isn’t serious. In older cats, the opposite is often true. Appetite without weight maintenance usually means the body is working against itself.
I’ve also seen well-meaning owners free-feed unlimited food, thinking more calories will help. In metabolic diseases, this rarely works and can worsen symptoms like vomiting or diarrhea.
What I Recommend Based on Real Cases
For a 17-year-old cat losing weight despite eating, I strongly recommend baseline bloodwork, including thyroid testing, kidney values, and glucose. In my practice, these tests have answered the question more often than not.
I’m cautious about telling owners to “wait and see” at this age. Senior cats compensate well until they suddenly don’t. I’ve seen cats go from mildly thin to critically ill in a short span because early signs were brushed aside.
When treatment is possible, I’ve watched cats regain weight, improve muscle tone, and become more comfortable. When it isn’t, identifying the cause still helps owners make informed, compassionate decisions rather than guessing.
The Bottom Line From the Exam Room
A 17-year-old cat who is losing weight but still eating is telling you something important. In my years of practice, this pattern has almost always led to a diagnosable medical condition, not just aging. Appetite alone is a poor measure of health in senior cats.
The cats who do best are the ones whose owners act while the cat still seems “mostly fine.” Those are the cases where I’ve seen meaningful improvement, not just more extended life, but better days.