Obesity in cats: a global epidemic and a silent threat to health

Obesity is now the most common metabolic disorder in domestic cats. It is estimated that between 30% and 60% of cats living in our homes are carrying extra weight. A “fluffy” cat may look endearing, but veterinary medicine (in line with WSAVA and AAFP standards) is unambiguous about it: obesity is a chronic inflammatory disease that drastically lowers quality of life and shortens it.

Knowing how to spot the problem, how to take weight off safely and why “slimming by eye” can be dangerous — even fatal — is the foundation of responsible cat care.

How to tell whether your cat is obese: the BCS scale

Vets do not judge body weight by the scales alone; they rely above all on the BCS (Body Condition Score), most often in its 9-point version. It gives an objective assessment of body fat regardless of the animal’s skeletal frame.

• BCS 4–5 (ideal): the ribs are easy to feel under a thin layer of fat, the waist is clearly visible from above and the abdomen is tucked up.
• BCS 6–7 (overweight): the ribs are hard to feel, the waist is barely defined and the belly is starting to round out.
• BCS 8–9 (obesity): the ribs cannot be felt under a thick layer of fat, there is no waist, the belly clearly sags and fat deposits appear at the base of the tail and on the limbs.

A simple test at home: run your hands gently along the sides of your cat’s chest, without pressing, and try to feel the ribs. If you cannot find them, your cat needs a change of diet.

Why do cats put on weight? The positive energy balance

The basic cause of obesity is a positive energy balance: more calories go in than are used up. In cats, however, several key factors shape how this plays out:

1. Neutering and spaying: the procedure is essential, but it cuts energy requirements by 20–30%. If you do not reduce the food portion after surgery, your cat will inevitably gain weight.
2. Low physical activity: indoor cats often eat out of boredom, and their only exercise is the walk to the bowl.
3. Feeding mistakes: scraps from the table, treats handed out without counting, and the “full bowl” method (constant access to dry food).
4. Breed predisposition and age: cats aged 5–12 are most at risk. Breeds such as the British Shorthair, Persian, Ragdoll and Maine Coon are naturally less active and lay down fat more readily.

The risks: why obesity is an inflammatory state

Fat is not a passive energy store — it is an active secretory organ that produces pro-inflammatory cytokines. Obesity in a cat means the body is permanently inflamed, which leads to:

• Type II diabetes: obese cats are several times more likely to develop insulin resistance.
• Hepatic lipidosis (fatty liver): a life-threatening condition that, paradoxically, is most often triggered when an obese cat stops eating too abruptly.
• Joint degeneration and chronic pain: excess weight destroys joint cartilage, and a cat in pain moves even less, which closes the vicious circle.
• Urinary tract disease: a heavier cat uses the litter tray less often and produces more concentrated urine, which encourages stone formation.

How much should a cat eat? The arithmetic of weight loss

Effective weight loss calls for precision. Veterinarians work out a cat’s resting energy requirement (RER — Resting Energy Requirement) using the formula:

$$RER = 70 times (text{body weight in kg})^{0,75}$$

An example: a 5 kg cat has an RER of roughly 234 kcal. During a weight-loss programme the vet sets the diet at about 60–80% of that figure — say 180–190 kcal a day. Remember: weighing the food on kitchen scales, to the gram, is the only method that genuinely works. Measuring cups can be up to 20% out.

The golden rules of safe weight reduction

The most important rule is a safe pace. A cat must not lose weight rapidly, because that risks the hepatic lipidosis described above.

• Pace: safe weight loss is 0.5% to 2% of current body weight per week.
• Diet: wet foods high in protein and low in carbohydrates are preferred. Wet food is less energy dense, so the cat can fill up on a larger portion.
• Frequency: split the daily ration into 4–5 smaller meals. This keeps glucose levels steady and cuts down on begging.

Active feeding and hunting stimulation

A calorie deficit is only half the battle. To get the metabolism going you also need movement — but movement that suits a cat’s nature.

1. Puzzle feeders: instead of serving food in an ordinary bowl, use toys the cat has to work at to get the kibble or meat out. This stretches out mealtimes and gives the mind something to do.
2. The “hunting” strategy: hide small portions of food around the house so your cat has to move and climb to find them.
3. A daily play session: at least 10–15 minutes of vigorous play with a wand or feather toy, finished off with a meal (this completes the hunting cycle).

Prevention: better than cure

If your cat is at a healthy weight, do everything you can to keep it there. Slimming down an obese cat takes months, whereas prevention needs nothing more than discipline:

• Regular weighing: put your cat on the scales once a month. A gain of 200–300 g in a cat is the equivalent of several kilograms in a person.
• Treats under control: every extra morsel has to be counted into the daily total and must not exceed 10% of daily calories.
• Monitoring after neutering: cut the calorie content of the diet by 20% straight after the procedure, rather than waiting for the first signs of weight gain.

Remember that any weight-loss diet should be discussed with a veterinarian or a veterinary nutritionist, so that your cat does not run short of key nutrients such as taurine or the B vitamins.

Based on WSAVA, AAFP and ESVCN guidelines.