How to Fatten Up a Skinny Kitten

Getting a kitten is exciting, but they are at an age where a healthy diet is very important. Nutritional deficiencies or too few portions can lead to physical deformities, stunted growth, and other health issues.

How to fatten up a kitten

What can I give my kitten to gain weight?

The best foods for kittens to gain weight are those with a high-calorie content. You want to choose a brand that provides a high-calorie count but doesn’t skimp on the protein or calcium as these are essential for healthy bone and muscle development.

Brands such as Wellness or Instinct are great for weight gain and they are also free from grain, corn, wheat and soy. Feeding a mixture of wet and dry will add some variety for your kitten. Try feeding wet food in the morning and giving your kitten access to dry kibble throughout the day. Patés tend to provide a higher kcal value than canned wet food. Always check the label before purchasing.

If your kitten is on a high-calorie diet but doesn’t seem to be gaining much weight, you could try supplementing their diet with nutritional gel. These are generally given on prescription from a veterinarian for cats suffering from a medical condition, but you can also purchase high-calorie gel from certain pet stores or your vet surgery.

How to fatten up a kitten

If your kitten has seen a vet and does not have any underlying health problems, you need to begin to slowly build up their weight. Adding weight too quickly can cause organ, muscle and bone damage.

If the lack of weight is simply a dietary issue, then increasing the portions slowly will allow your kitten to gradually gain weight. Ideally, your kitten should be eating little and often, so aim for 3 or 4 small meals per day. If you cannot fit this into your daily routine, try purchasing an automated feeder which can be programmed to release food at pre-set times.

Veterinarians may suggest a higher-calorie diet. When switching diets, you need to do this slowly over at least one week to reduce stomach upset. Start by adding a tablespoon of the new food into your kitten’s current diet. If your kitten eats all the food and has no side effects, you can gradually increase the amount of new food each day.

It is important that you keep up with your kitten’s regular worming schedule. Internal parasites take a lot of the nutrients from the food your kitten eats, which means your kitten becomes deficient.

Why is my kitten so skinny but eats all the time?

A cat that eats well but doesn’t gain weight may have an underlying health problem. If the problem isn’t identified and treated, it can lead to malnutrition, which can be fatal.


Parasite infections can make your kitten lose weight even though he’s eating a lot of food because the parasites rob nutrients from his body. Parasites include worms such as tapeworms, roundworms, and hookworms. These parasites can also cause severe diarrhea in some cases.


Another common reason for eating too much but not gaining weight is hyperthyroidism. This disease causes cats to lose weight despite their ravenous appetite.


Cats that develop diabetes can appear hungry all the time but still lose weight. You might notice your cat drinking and peeing more frequently than usual. Your vet can diagnose the condition with a simple blood test; insulin injections are needed to control it.

You should definitely consult with your vet if you notice that your cat is losing weight despite an insatiable hunger.

Why is my kitten not gaining weight?

The first step is to have your kitten checked by a veterinarian to rule out an underlying illness. If your kitten is declared fit and healthy, you can start to look at other possible causes.

Nutritional deficiencies

Each pet food company has its own recipes and uses different ingredients. Underweight cats may not be getting enough natural fats in their diet, so you could try switching to a high-calorie kitten food.

Portion sizes

You may be feeding a good quality diet already, but simply not giving enough of it. Most pet food labels have a food guide for each age, but if your kitten is not gaining weight, you may need to feed a little more. Remember, these guides are a general guideline and not set in stone. Every cat is different.

Outdoor cat

This one is pretty obvious. Outdoor cats use more energy than indoor cats, so they need more nutrients. Outdoor kittens should be fed a higher calorie diet with larger or more frequent portions.


There are many different cat breeds, just like there are different dog breeds. Some cats are stocky and plump, whereas others are lean and tall. Your kitten may be a breed that has a slim frame and carries very little extra weight. This is totally normal.

Age makes a difference

Just like humans, kitty teenagers tend to go through a ‘lanky’ phase. This is the part of their life when they experience a sudden growth spurt. They will grow taller and longer so they appear skinny. As long as they are not losing weight and have a good appetite, then there is nothing to be concerned about.

How can I tell if my kitten is underweight?

It can be discomforting to think that your kitten is underweight, but there is a simple and reliable guide that will help you check without needing a trip to the vet. Most pet food companies use a similar guide on their packaging.

Body conditions are given a rating from 1 to 9, with 1 being the thinnest and 9 being the most overweight. 1 to 4 fall into the underweight range and 6 to 9 fall into the overweight range.

  1. Ribs, spine and hip bones are visible, with no obvious fat. Very narrow waist/abdomen.
  2. Ribs, spine and hip bones visible on shorthaired cats, minimal muscle mass, no fat and narrow waist/abdomen.
  3. Ribs visible with minimal fat, spine noticeable on shorthaired cats, minimal fat around the abdomen.
  4. Ribs just visible, slight fat layer around the abdomen. Hip bones may be noticeable.
  5. This is the ideal body condition. Well proportioned with no visible ribs, spine or hip bones. Minimal abdominal fat and slightly noticeable muscle mass.
  6. Body shape appears plump with noticeable abdominal fat. No waist definition.
  7. Ribs not visible and no waist definition. The abdomen appears rounded or slightly sagging.
  8. Obvious excess fat around the ribs. Abdomen clearly rounded with noticeable fat.
  9. Heavy fat covering the entire body. Clear sagging of the abdomen and no noticeable waist.

Kittens should ideally be condition 5. A slim body, with a thin layer of fat and a noticeable waist towards the hips. Slim breeds may have slightly noticeable ribs.

Feeding a Starved Cat! Help Them Recover from Starvation.
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Hannah Elizabeth is an English animal behavior author, having written for several online publications. With a degree in Animal Behaviour and over a decade of practical animal husbandry experience, Hannah's articles cover everything from pet care to wildlife conservation. When she isn't creating content for blog posts, Hannah enjoys long walks with her Rottweiler cross Senna, reading fantasy novels and breeding aquarium shrimp.

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