✓ Veterinarian Reviewed
Reviewed by Dr Gloria Ebeyer (BAVBS, DVM, Grad Cert SAECC, MANZCVS [Veterinary Practice])
Last reviewed: June 2026
A healthy weight plays a big role in your cat’s wellbeing, but weight changes aren’t always easy to spot. Because weight gain or loss often happens gradually, your cat may become rounder or thinner before you realise something has changed.
Keep reading to find out all the main causes of weight gain in cats, as well as how to help your cat lose weight.
Key causes of weight gain in cats
Once your cat is fully grown (typically between 12 and 18 months), keep an eye on their weight to ensure they’re in an ideal range. Being overweight can affect their wellbeing, contributing to lower energy, joint pain, grooming difficulties and even a shortened lifespan.
Common causes of weight gain in cats include:
- Free feeding and grazing habits
- Consuming too many treats
- Low activity levels — often more noticeable in indoor cats
- Age-related metabolism slowdown, particularly in senior cats (9 years+)
- Post-desexing hormonal changes
Determining if your cat is overweight or underweight
First off, when it comes to finding out if your cat is overweight, don’t fret if it turns out they are. Many cats gain weight without it being immediately obvious - and if you have a long-haired or naturally larger cat, such as a Ragdoll or Maine Coon, it can be even harder to pick up on.
Similarly, If your cat is underweight but otherwise eating well, staying active and toileting normally, they may simply need more food — but check with your vet if you’re unsure.
Take a photo of your cat from above and from the side every few weeks. Small body changes can be easier to notice when you compare photos over time, especially for fluffy cats.
Ideal weight ranges per breed
A good starting point is the ideal weight range for your cat’s breed:
- Domestic shorthair - 3.5 to 5kg
- Domestic longhair - 3.5 to 5kg
- Maine Coon - 4.5 to 11kg (females tend to be on the lower end)
- Ragdoll (as well as Ragamuffin) - 4.5 to 9kg (females tend to be on the lower end)
- Siamese - 3 to 5kg
- Burmese - 3.5 to 5.5kg
- Persian - 3.5 to 5.5kg
- Bengal - 3.5 to 7kg
- British shorthair - 3.5 to 7kg
- Abyssinian - 3 to 5kg
- Sphynx - 3.5 to 5.5kg
These ranges are only a guide. Your cat’s ideal weight depends on their breed, body shape, sex and whether they’re a crossbreed, so it’s best to confirm with your vet.
If you’re a Petstock member, you can also get free nurse weight checks for your feline friend to keep track. Most of our Petstock locations also include a scale in front or inside of the store, so you can pop in to weigh them at any time.
Body check
These quick body checks can help you assess your cat’s condition at home:
- Feel the ribs: Run your fingers along your cat’s ribcage, located just behind their front legs. If they’re at an ideal weight, you should easily feel the ribs, but they should not be sharply visible. If the ribs are prominent (visible), this likely means your cat is underweight. If you cannot easily feel the ribs, this means your cat may be overweight.
- Look for a waist: Look down at your cat from a bird’s-eye view while they’re standing. If your cat is in an ideal weight range, you’ll notice a slight inward curve behind their ribs. If there’s a significant inward curve, that likely means they’re too thin. If there is no inward curve (they look barrel-shaped) or a noticeable outward curve behind the ribs, they’re overweight.
- Check for an abdominal tuck: This check is performed from a side view of your cat while they’re standing up. When a cat is at an ideal weight, their belly should slope gradually upward between their ribs and hind legs. If the upward slope is overly pronounced, it likely means they’re underweight. If there is no gradual upward slope (their belly is sagging), they’re overweight.
These checks can give you a clearer picture than weight alone.
How to help your cat shed additional weight
The best place to start with an overweight cat is in managing their calorie intake and getting them moving more often.
If you free feed your cat (e.g. you leave out a bowl stacked full of kibble), implement measured meals that are given throughout the day. If you’re not physically present during the day, consider investing in an automatic feeder that can dispense kibble at set amounts in your absence.
Puzzle or slow feeders can help cats eat more slowly, making it easier for them to recognise when they’re full. Also swap out calorie-dense treats with healthier alternatives.
Vet-recommended weight management foods, including fibre-rich kibble and nutrient-rich wet food, can help your cat feel fuller and support their energy levels.
Finally, exercise is important. Get your cat moving with daily play sessions to boost their metabolism and promote weight loss.
Helping your cat increase their weight
On the other end of the scale, if your cat is underweight, it’s often about slowly increasing their caloric intake until they reach a stable weight.
Focus on nutrient-rich foods, temporarily increase dry food if suitable, and support digestion with prebiotics, probiotics and fibre.
Proper hydration through wet foods or water also helps with weight management .If they’re not interested in water, try adding water to wet food or a small amount of juice from canned plain tuna to their bowl.
It’s also worth noting that even hairballs can impact your cat’s appetite. So, if they regularly have issues with these, look into hairball treatments, as well.
When to see a vet
Book a vet appointment if your cat is significantly over or underweight, experiences sudden weight gain or loss, or doesn’t respond to changes in diet and exercise. While weight changes can often be managed with food and activity, they can sometimes point to an underlying health issue.
Keep your cat happy and healthy
Want to help your cat maintain a good weight and healthy digestive system? Shop the selection of Cat Prescription and Vet Diet foods at Petstock today.