Signs your pet is overweight: ribs, waist and body condition

The quickest home test for excess weight is the ribs. On a dog or cat at a healthy weight they can be felt easily under a thin layer of fat, much as the bones on the back of a hand can be felt under the skin. If finding them takes firm pressure, the animal is carrying more fat than it should, even if it looks normal at a glance.

How common excess weight is

Very common, and easy to miss. The Merck Veterinary Manual estimates that more than half of the dogs and cats seen by veterinarians in the US are overweight or obese. It defines overweight as 10% to 20% above ideal body weight and obesity as more than 20% above it. So a dog whose ideal weight is 20 kg (44 lb) counts as obese above about 24 kg (53 lb), a gain that does not look dramatic in a thick coat.

Owners who live with the animal every day are poorly placed to notice gradual change. In a study of 309 dogs at two French veterinary teaching hospitals, 35% were overweight, and the strongest factor linked to being overweight was an owner who underestimated the dog's body condition. Scoring the body by hand, rather than judging by eye, gets around that.

Seven signs of excess weight

1. The ribs are hard to feel

Stand behind or beside the animal, put your thumbs along the spine and spread your fingers over the rib cage. Stroke lightly. Each rib should be distinct without pressing. If there is a soft layer between skin and bone, like the fleshy pad of a palm, there is too much fat. If the ribs cannot be found at all, the animal is well into the obese range.

2. No waist from above

Look straight down on a standing dog or cat. Behind the ribs the body should narrow before widening again at the hips. An overweight animal is the same width from chest to hips, or widest in the middle.

3. The belly hangs

From the side, a lean dog's underline rises from the bottom of the chest toward the hind legs. That rise, the abdominal tuck, flattens out as fat builds up and then disappears, and in heavy dogs the belly may sway when they walk. Cats complicate this check. Many have a primordial pouch, a flap of loose skin between the hind legs that swings when they trot and is normal at any weight. The pouch sits at the back of the belly; fat thickens the whole abdomen and hides the ribs as well.

4. Less willing to move

Carrying extra weight makes exercise harder work. A dog that used to finish its walk starts lagging or sitting down; a cat stops jumping onto the shelves it used to use. Less activity burns fewer calories, so the weight tends to climb further. Stiffness can look the same, and in heavy animals the two often come together, since excess weight is linked to arthritis.

5. Heavier breathing

Fat around the chest and abdomen restricts breathing. Watch for panting after light exercise, poor tolerance of warm weather, and new or louder snoring. Flat-faced breeds such as Pugs, Bulldogs and Persians already have narrowed airways, so extra weight affects them sooner. Breathing trouble at rest, or a dog that collapses on a warm day, needs a vet the same day, whatever it weighs.

6. Unkempt fur on the back and tail (cats)

A heavy cat may be unable to twist far enough to groom its lower back, the base of its tail and around its bottom. The coat there becomes greasy, flaky or matted while the front half stays clean. Arthritis can cause the same pattern, so it is worth mentioning to a vet rather than assuming weight is the only reason.

7. The collar needs letting out

Fat collects on the neck and chest as well as the belly. If a collar that used to fit now feels tight at the same setting, measure the neck and weigh the animal. Two fingers should slide under a correctly fitted collar.

Body condition scoring

Vets turn these checks into a body condition score. The WSAVA body condition chart uses a 9-point scale, and the version for cats works the same way.

• 1 to 3, too thin: ribs, spine and hip bones visible or easily felt with no fat over them; loss of muscle at the low end.
• 4 to 5, ideal: ribs easy to feel under a thin fat cover, a waist visible from above, the abdomen tucked up from the side.
• 6 to 7, overweight: ribs felt under excess fat (with difficulty at 7), the waist less distinct or gone, and at 7 fat over the lower back and base of the tail.
• 8 to 9, obese: ribs not felt, no waist, a rounded or hanging abdomen, and fat on the neck and limbs.

Scoring once a month at home, at the same time as a weigh-in, shows a trend long before a new collar hole does. Vets also check muscle over the spine, hips and shoulders, because an older or ill animal can lose muscle while keeping its fat.

What the extra weight does

The conditions linked to excess fat cover most body systems. Merck lists shorter life expectancy, chronic inflammation, heart and lung problems, heat and exercise intolerance, arthritis, weaker immune function, pancreatitis in dogs, and diabetes and fatty liver disease in cats. VCA Animal Hospitals adds cancer, high blood pressure, bladder stones and a higher risk of complications under anesthesia.

Two studies give a sense of scale. In a US study that followed 1,457 cats for four and a half years, obese cats were 3.9 times as likely as cats of optimal weight to develop diabetes and 4.9 times as likely to need veterinary care for lameness. In dogs, the best-known evidence comes from 48 Labrador Retrievers raised in pairs. One dog in each pair was fed 25% less than its pair-mate from 8 weeks of age for life. The leaner dogs had a longer median life span, and signs of chronic disease generally appeared later. Portion size alone, over a lifetime, made a measurable difference.

Why dogs and cats gain weight

Energy in exceeds energy out. The usual sources of the surplus are ordinary ones:

• Portions set by eye or by the bag. Feeding guides on packaging cover a wide range of dogs or cats, and a scoop is an imprecise measure. Food left out all day for cats to graze is a major cause of feline obesity, according to Cornell's Feline Health Center.
• Treats and table food. Merck and VCA both advise keeping treats under 10% of daily calories. In a household where several people give snacks, that limit is passed without anyone noticing.
• Neutering. Merck lists neutering as a risk factor, so portions are worth reviewing in the months after the operation rather than left as they were.
• Age and less exercise. Activity tends to fall with age, and indoor cats and dogs with short daily walks have little room for extra food.
• Medical causes. An underactive thyroid in dogs, Cushing's disease and long courses of corticosteroids can all cause weight gain, which is one reason a vet should examine the animal before a diet starts.

Losing weight safely

Start with a vet visit

A vet can rule out the medical causes above, confirm the body condition score, estimate an ideal weight and set a daily calorie target from it. This matters most for cats, for animals scoring 8 or 9, and for any animal with another illness. Cornell advises that any feline weight-loss program be carried out under a vet's direction.

Weigh the food

A kitchen scale in grams is more accurate than a cup or scoop, especially for small dogs and cats whose whole day's ration is a few tablespoons. Weigh out the daily amount each morning, and take treats from that allowance rather than adding them on top.

Consider a weight-loss diet

Cutting a normal food sharply also cuts the vitamins, minerals and protein that come with it. Diets made for weight loss are designed for restricted feeding. Merck describes them as higher in protein and fiber, with added L-carnitine. Veterinary weight-loss diets are the usual choice for animals that need to lose a lot.

Add activity gradually

For dogs, lengthen walks a little at a time and watch for stiffness or lagging the next day, particularly in heavy or older dogs whose joints may already be sore. For cats, short play sessions with a wand toy several times a day suit the way they hunt. Puzzle feeders slow eating down and turn part of a meal into exercise for both species.

Weigh every two weeks and adjust

Merck suggests weighing every 2 weeks and adjusting the plan if needed based on the response. A reasonable pace is about 1% of body weight a week; Cornell gives 1% to 2% a week for cats. For a 30 kg dog that is roughly 300 g a week.

Sources

1. Nutrition in disease management in small animals (obesity section). Merck Veterinary Manual.
2. Prevalence and factors associated with overweight and obesity in dogs presenting to French university veterinary teaching hospitals during the COVID-19 pandemic. Topics in Companion Animal Medicine, 2024.
3. Body condition score (dog). World Small Animal Veterinary Association.
4. Obesity in dogs. VCA Animal Hospitals.
5. Associations between body condition and disease in cats. Journal of the American Veterinary Medical Association, 1998.
6. Effects of diet restriction on life span and age-related changes in dogs. Journal of the American Veterinary Medical Association, 2002.
7. Obesity. Cornell Feline Health Center, Cornell University College of Veterinary Medicine.