Fattening Up A Cat – How To Help A Cat Gain Weight

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  • How do I fatten up an underweight cat?

    It is critical to determine if the cat has an underlying medical condition that has caused him or her to be underweight. Once the cause (if any) has been diagnosed and addressed, the appetite should return in most cases.

    The goal is to stimulate the cat’s appetite and increase calories. Below are some ways to help fatten up a cat.

    Tips to fatten up a cat

    • Switch to kitten food: Kitten food is higher in calories than adult food.
    • Feed several times a day: Feed smaller portions frequently throughout the day.
    • Add calories: Include a little grated cheddar or parmesan cheese or plain yoghurt to the top of the cat’s food.
    • Switch to wet food: Canned cat food is more appealing than dry. Feed 3-4 times a day while you are trying to increase weight and leave dry food out for your cat to nibble on between meals.
    • Try a homemade diet: If canned food isn’t an option, consider a homemade diet, at least for the short term, this may be raw or cooked. Include muscle meat, as well as chopped heart, liver, and kidneys. Foods that are highly appealing to cats include cooked chicken breast cut into pieces, minced beef or chicken, tuna, and liver. Tuna and liver are okay to give to a cat who has lost his appetite, but they should not be given for more than a day or two as they can cause medical issues.
    • Warm the food: Heat food to body temperature, to produce a stronger smell.
    • Feed a high-quality brand of food: Cheaper brands have more fillers and don’t offer the cat a lot in the way of nutrition.
    • Prescription diets: Your veterinarian can recommend brands of food to help gain weight in cats. Hills a/d comes in dry and canned form, is high in calories and digestible proteins.
    • Syringe feed: If your cat has a poor appetite, try syringe feeding a highly palatable wet food.
    • Nutritional supplements: Speak to your veterinarian about nutritional supplements such as Nutrical or Nutri-Stat that can get extra calories in and help to kick-start your cat’s appetite.
    • Feed cats separately: If you have several cats, feed the underweight one in a separate room to ensure he gets enough food. Sometimes more dominant cats can hog the food bowl.
    • Appetite stimulants: If all of the above methods fail, speak to your veterinarian who can prescribe appetite stimulants. These medications are especially useful to treat loss of appetite due to illness or chemotherapy.

    Causes of weight loss in cats

    • Sickness which causes a loss of appetite (anorexia)
    • Stress, fussiness, inter-cat issues
    • Weight loss despite a healthy appetite and no underlying disease (not enough food, nursing queen and loss of muscle mass as the cat ages)
    • Weight loss due to a medical condition but not related to loss of appetite (hyperthyroidism, acromegaly, malabsorption disorders such as exocrine pancreatic insufficiency and inflammatory bowel disease)


    Medical causes occur most often in middle-aged to senior cats, the majority of which cause the cat to lose weight due to a poor appetite. Hyperthyroidism, on the other hand, speeds up the cat’s metabolism. Despite a normal to increased appetite, the cat continues to lose weight.

    Hyperthyroidism: Caused by a benign hormone-secreting tumour of the thyroid gland, which causes the metabolism to speed up.

    Diabetes: A common endocrine disease where the cells build up a resistance to insulin, a hormone necessary for glucose to enter the cells. As a result, glucose levels build up in the bloodstream.

    Chronic kidney disease: A gradual loss of kidney function over months or years, which causes a build-up of toxins in the blood. Senior cats are very prone to developing kidney disease.

    Cancer: There are many types of cancer in cats; most cancers will cause your cat to feel unwell, which in turn leads to anorexia and weight loss. Tumours can grow in the cat’s mouth, creating discomfort when he eats.

    Parasitic worms:  Cats are prone to several types of parasitic worms. Tapeworm and roundworm are the most common intestinal worms in cats. These parasites compete with the cat for food.

    Nursing kittens: A lactating queen (mother cat) uses enormous resources to provide nourishment to her kittens. Over time can lead to her losing weight if she is not receiving an adequate amount of food.

    Mouth ulcers: A mouth ulcer (or mouth sore) is a painful, open sore that can affect the gums and tongue.

    Cryptosporidium and Giardia: Parasitic infections caused by single-celled protozoa resulting in vomiting and diarrhea.

    E. coli: A bacterial infection of the intestinal tract leading to vomiting and diarrhea.

    Inflammatory bowel disease: A leading cause of vomiting and diarrhea in cats, IBD is a group of disorders caused by the infiltration of inflammatory cells in the intestinal tract resulting in poor digestion and absorption of food.

    Cat flu: Several types of pathogens can cause flu in cats. Symptoms typically affect the upper respiratory tract, which can result in a loss of appetite as the cat loses its sense of smell.

    Stress: Cats are susceptible to changes in the routine, household, bullying from other cats.

    This list is by no means extensive; there are many other medical causes. Read here for more causes of weight loss in cats.


    The veterinarian will perform a complete physical examination of your cat and obtain a medical history from you.

    Diagnostic workup:

    Additional tests will depend on results of baseline tests but can include:

    • Imaging studies (X-ray and ultrasound): To evaluate the organs and look for signs of intestinal blockages or tumours.
    • T3 and T4 tests: To evaluate for hyperthyroidism.
    • Fecal studies: Microscopic evaluation of a sample of feces to look for parasitic eggs.


    • Julia Wilson, 'Cat World' Founder

      Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio