Since many of the cats we see are also overweight, their normal weight pet parents may appear unusually thin. It can also be very difficult to tell if your cat is thin if its hair is long or its belly is sagging.
If you think your kitty needs to gain weight, you should first take them to the vet to rule out any underlying medical conditions. If no health problems are found, the suggestions below can be very helpful in getting your cat back on track and gaining weight.

Healthy cats may require more food per day and/or a lot of free access to dry food to gain weight. Cats like to ‘graze’ or eat small meals throughout the day, so having food available throughout the day can make a big difference. Be sure to check with your veterinarian to see if this would be a good option for your cat. Free choice feeding can also lead to obesity and is only recommended in certain circumstances.
If you have more than one cat, one may be guarding the food while the other is unable to stop herself from eating her fill. Make sure all cats have access to food throughout the day in a safe, non-threatening environment.
If your cat is nervous, make sure the food bowl is not near any object that scares them, such as a bicycle furnace, air conditioner, noisy pipe, or barking dog.
If you feed your cat dry food, give them canned food in addition to the dry food.
If you decorate their food with toppers and give your cat treats at mealtime, you can provide simple food straight from the bag or in a quiet area without any hassle.