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How to Help an Underweight Cat Gain Weight

Knowing the reason behind why your cat is underweight is the first step to helping her get healthy again.
Toby Amidor, MS, RD, CDN, FAND By Toby Amidor, MS, RD, CDN, FAND Medically Reviewed by Alicen Tracey, DVM January 10, 2022 Medically Reviewed by Alicen Tracey, DVM Advertisement Pin FB More Tweet Email Send Text Message Print
how to make a cat gain weight mom and son feeding cat at kitchen table with feline fine logo Credit: filadendron / Getty

Although many cats may be overweight, there are cats who are underweight and need to put on a few pounds. Below are instances where your cat may need to gain weight and recommendations for how to do so.

Does Your Cat Need to Gain Weight?

There are several reasons why your cat may need to gain weight. According to Catherine Lenox, DVM, DACVIM (Nutrition), Regulatory Veterinary Manager and a Board Certified Veterinary Nutritionist at Royal Canin North America, "If you notice your cat losing weight, the most important thing to do is to talk to your veterinarian." If you see your cat, even an obese cat, is rapidly losing weight it can be a sign of a serious health issue—which can decrease appetite and result in weight loss—including:

Hyperthyroidism (cats often lose weight while still eating well)
Inflammatory bowel disease (IBS)
Pancreatitis
Liver disease
Kidney disease
Respiratory or nasal disease
Dental disease
Conditions like osteoarthritis that cause pain over time

If your cat has stopped eating, it's important to contact your veterinarian for advice right away, even if you haven't noticed weight loss. Cats who have stopped eating—especially obese cats—are at risk for a serious condition called hepatic lipidosis, sometimes called "fatty liver." This liver condition can lead to serious complications and requires urgent medical care.

Lenox also says that you may see the weight loss occur over time with the duration of signs lasting longer than two to three weeks. "Slow, steady weight loss over time can also be problematic, and any cat losing weight should be assessed by a veterinarian."

When it comes to older felines, "It is not normal for a healthy senior cat to be underweight just simply due to age," Lenox says. "If your older cat is losing weight, especially if you haven't changed their diet or feeding amount, you should consult your veterinarian to look for underlying health conditions. Cats are really good at hiding health issues, and uncovering health issues can help guide diet selection and feeding amounts, regardless of your cat's age."

You may also have chosen to adopt a rescue cat, and there can be issues with rescue cats being underweight. According to Andrea Herrick, founder of PRoud rescuers of PR where cats and kittens are rescued from the streets of Puerto Rico, "Most (if not all) of the cats are underweight due to two primary reasons: malnourishment (due to lack of appropriate nutrition in the streets) or some sort of illness. Most of the time, their insufficient weight is due to both," Herrick says.

There is also an assessment tool that veterinarian's use to decide whether a cat is overweight or underweight called the body condition score. "Veterinarians aim to keep cats around a body condition score of four to five out of nine, with one out of nine being extremely emaciated and nine out of nine being extremely obese. The body condition score can be assessed at each veterinary visit and is an assessment of body fat," Lenox explains.

How Much Should You Feed Your Cat to Help Them Gain Weight?

Your veterinarian may recommend a specific diet to help your cat gain weight. "In general, diets designed for weight gain are calorie dense, meaning that a smaller volume of food is required to get in the necessary calories for weight gain. Calorie dense foods tend to be high in fat because fat contains more calories per gram versus protein or carbohydrate," Lenox explains. You should also ask your vet which is the best diet for your cats weight gain as some medical conditions require a more specific type of diet.

In some cases, a temporary or long-term feeding tube may be called for to help the cat gain weight. This type of feeding can also be used to "help reduce a pet owner's stress about whether or not their cat will eat and can also be used to administer some medications," Lenox explains.

According to Maryanne Murphy, DVM, PhD, DACVIM, Clinical Assistant Professor of Nutrition at the University of Tennessee College of Veterinary Medicine, there can also be individual variation between cats and "this is why it is so important to critically assess the diet history to determine how many calories the cat is reliably eating and to determine an accurate estimation of the cat's ideal weight." Murphy explains that "if the cat appears to be eating an appropriate calorie amount for its ideal weight but is still considered underweight, then we generally will increase intake in 10–20 percent increments, depending on how much weight the cat needs to gain. In some cases, we may even recommend free choice feeding, but it is important to record how much the cat actually consumes. It is very easy to assume your underweight cat is eating a lot more food than it actually is in this situation."

Once you and your vet determine how much food your cat needs, determining how often you feed your cat is the next step. Herrick recommends instead of feeding once or twice a day, feed your feline small meals several times a day and provide them with a clean source of fresh water to drink throughout the day.

RELATED: This Is What an Average Cat Should Weigh

5 Healthy Ways to Help Your Cat Gain Weight

Lenox and Herrick recommend the following tips when it comes to helping your cat put on a few much-needed pounds.

Feed your cat canned food: Canned cat food is made with meat, giving it a more enticing taste and smell for your cat than a dry food. And all that extra moisture helps get more water into your cat's diet, making it a win-win for keeping kitty fed and hydrated.
Gently warm your cat's food: Your cat may prefer food that is slightly warmed, not too hot.
Try hand feeding your cat: This may also help encourage the cat to eat food. Petting your cat may also help.
Change up the food: Cats do have preferences regarding taste so change it around. Herrick suggests offering a tuna meal if what they usually eat is chicken, or vice versa. Always remember to change to new food gradually, so as not to upset their stomach.
Ask about a supplement: Discuss with your veterinarian if a vitamin or mineral supplement or high calorie supplement is necessary for your cat at this time.

RELATED: Top Food Choices to Help Cats Lose Weight

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