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Fatty Liver Syndrome: Why You Must Never Crash-Diet a Cat

If your cat hasn’t eaten for 48 hours or more, head straight to the vet.

A non-eating cat’s liver goes into overdrive to give the body energy — sometimes with disastrous results. By: jimmy brown

Is Lucky carrying too many layers of love?

The outsized cuddly cat could do with losing a few pounds, but there’s a right and wrong way to go about this.

Cats are unique (in so many ways) because starvation can trigger a serious complication called hepatic lipidosis (HL), also known as fatty liver syndrome (FLS).

Be Watchful

Fatty liver syndrome isn’t confined to textbooks and rare cases; it can happen to any cat. Given a perfect storm, where all the risk factors stack up, any cat is at risk.

With this in mind, it pays to understand FLS so you can be alert for those vital warning signs and seek prompt treatment.

Fudge: An Outsized Cat Who Lost Her Appetite

Fudge sticks out in my mind as a “textbook” FLS case. Also, how ironic that a cat called Fudge should be so roly-poly!

Anyhow, Fudge is a good example of an FLS patient in waiting. At each booster visit, Fudge would weigh heavier than in the previous year. Each year, her person and I would exchange glances and chat about the dangers of carrying too much weight. Each year, we’d reach an accord to try portion control and puzzle feeders … to no avail.

So when I saw Fudge was booked in for “not eating,” I was already concerned. The story was a familiar one: Fudge had gone off her food a few days earlier. But as Fudge had plenty of reserves, her human decided to wait and see what happened.

Unfortunately, this was the wrong thing to do: After just 3 days of no appetite, Fudge was disproportionately sick. She was vomiting, dehydrated and had a yellow tinge to her gums. Her liver also felt enlarged.

Fudge was admitted for tests, and everything pointed to HL. She was given drugs to stop the vomiting, pain relief and intravenous fluids, and a feeding tube was placed. All we could do then was wait and see if she recovered.

A good diet and plenty of exercise can help cats avoid obesity-related problems. By: temaki

Fatty Liver Syndrome

FLS is a complication of not eating. It occurs when the body needs energy and the liver mobilizes its fat reserves. The problem is, too much fat is released from the liver cells at once and floods the liver. Think of this like a crowd of people trying to exit a room through a small door, with yet more people piling in behind them.

The overwhelmed liver is so saturated with fat that it can’t do its daily work of detoxing blood, producing clotting agents and managing protein levels. Now, in addition to the primary problem (poor appetite), the cat has hitched a ride on a downward spiral of liver failure. Left untreated, complete organ failure is likely, resulting in death.

Diagnosis and Treatment of FLS

Fudge not eating and taking a turn for the worse gave me a lot of clues. Then a physical exam with jaundice and an enlarged liver pushed my thinking further down that road.

The final puzzle piece was the cat’s blood. When it was spun down, it was more likely runny butter than blood, with sky-high liver enzymes, raised bilirubin and signs of dehydration. In a perfect world, I’d have scanned Fudge’s liver to check for tumors, but due to restricted finances, the client decided that I should treat Fudge and then see what happened.

Treatment includes:

  • Correcting the underlying cause of poor appetite. For Fudge, a rotten tooth proved the initial culprit.
  • Intravenous fluids: to correct dehydration.
  • Anti-nausea medication: to control vomiting.
  • Vitamin injections: to boost levels of Vitamins B and K, which fall in liver disease.
  • Antibiotics: if infection is suspected.
  • Pain relief: to manage underlying discomfort.
  • Force-feeding: giving the body energy as food helps switch off fat release from the liver.

Learn a little more about cats’ liver functions in this video:

YouTube player

What to Watch For

Long story short: If your cat is unwell and stops eating, keep a close eye on them. FLS can develop after just 3–4 days of starvation; if your cat’s appetite drops off, don’t wait to see what happens. There is a risk of serious complications.

Signs that FLS is occurring include:

In particular, cats with pre-existing health problems are at greater risk. These may include:

  • Overactive thyroid glands
  • Diabetes
  • Renal disease

Experts also cite obesity as a risk factor. This makes sense — with the body tissue already over-endowed with fat, it’s even harder to cope when more floods the system.

Fudge’s Future

I’m happy to say, after several days’ hospitalization, Fudge did very well. For a while, when she felt better, she entered a sort of fat-cat heaven, where she was being force-fed food through the tube. Pretty soon, she got her mojo back and started snacking for herself.

Fortunately, her human took this episode to heart. When Fudge had fully recovered, she was put on a careful diet with measured portions and homemade puzzle feeders (muffin tins and toilet rolls) so Fudge worked for her calories. As the weight came off, Fudge also started to play with a wing-on-a-string, and she seemed to love this one-on-one time with her human every bit as much as eating.

So if your larger cat’s appetite dwindles, seek help sooner rather than later, and never leave any cat who’s not eating for longer than 48 hours without seeing a vet.


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Sept. 15, 2017.