Understanding your cat's optimal weight depends on her breed, body type, and overall health. If you can see her ribs and aren't able to feel any fat on her ribs or back, she's likely too thin. An underweight cat should see the vet to ensure she doesn't have a medical condition behind her lightweight frame.
Know if your cat's too skinny
Much emphasis is placed on the dangers of carrying excessive weight — joint disorders, diabetes, and shorter life span are among the health risks associated with obesity. However, underweight cats are also more susceptible to injury and illness, according to Kindness Animal Hospital.
If your cat is a long-haired breed, underweight can often go unnoticed. You might not realize your feline is wasting away unless you notice she's not eating or her coat becomes dull and harsh.
Although some cats are very finicky, others could have a hard time eating due to dental issues, pain, or other physical conditions not readily seen. Stress, anxiety, or changes such as a move, new pet, or remodeling the house could also cause your kitty to go off her feed. Take notice of any changes you see in your cat's behavior.
Be familiar with how much your cat should weigh. A Maine coon, for example, tips the scales at 10 to 25 pounds while a Siamese can be perfectly healthy at just 5 pounds, according to the Association for Pet Obesity Prevention.
Understand cat conformation
Cats come in different shapes and sizes, ranging between the extremes of two different body types or conformation_s: Oriental and cobby, according to the [ASPCA Complete Guide to Cats](https://www.google.com/books/edition//7JCTRdg68tIC?hl=en). Most mixed-breed domestic short-hair cats are a combination of the two body types. Characteristics of the Oriental build include
- svelte and fine-boned,
- long, slender limbs, and
- slender, pointed tails.
Traits of a cobby build include
- short-bodied, and
- shorter, stouter tail than the Oriental build.
As cats vary according to build, they also differ in appropriate weight ranges. The Siamese, with her Oriental build, typically weighs between 5 and 10 pounds. The Persian has a cobby build and usually runs between 7 and 12 pounds. A mixed-breed cat typically weighs around 8 to 10 pounds. Some cats are built more substantial, such as the Maine Coon, who runs between 10 and 25 pounds.
Size her up
- Very narrow waist
- Prominent rib cage
- Obvious shoulder blades
- Visible spine and ribs
If your cat has a long coat, it may be difficult to check her weight visibly; use your hands to gauge her weight. Stand behind her and spread your fingers over her ribs, while lightly pressing your thumbs on her spine. As you gently rub along her sides, you may feel indications she's underweight, such as:
- Lack of fat on her back or ribs
- Easily distinguished ribs and spine bones
A cat who is of proper weight should have a minimal fat covering on her back and ribs.
Get professional advice
If your cat is too skinny, she should see the vet. There are a host of medical conditions that can cause weight loss and wasting in cats, including:
- Hyperthyroidism — other symptoms include ravenous appetite, vomiting, and diarrhea
- Diabetes —also accompanied by drinking and urinating excessively
- Cancer — common signs include lethargy, appetite loss, and hiding behavior
- Gastrointestinal illness — to include diarrhea, vomiting and appetite loss
- Dental issues — often accompanied by loss of appetite and drooling
Organ failure, intestinal parasites, and feline infectious peritonitis also can cause weight loss. Additionally, a cat who's experiencing stress such as anxiety or depression can drop weight and become too thin.
A cat who loses too much weight is also vulnerable to hepatic lipidosis, also called fatty liver syndrome, according to WebMD. This is a potentially fatal condition causing the liver to use large amounts of body fat to for energy.