Obesity in Cats

In this guide

The most common nutritional problem among UK pets is simple overconsumption, too many calories leading to excess weight. Current estimates suggest between 39 and 52 per cent of British cats are overweight or obese.

A cat is classed as obese once it is at least 20 per cent above its optimal weight due to excess fat. “Overweight” covers the 10 to 19 per cent range above optimal. Ideally, cats should be fed to sit right at their optimal weight, since long-term research shows both obesity and excessive thinness cut life expectancy short.

How body condition is assessed

Health risks linked to obesity

Excess weight raises the risk of a wide range of conditions, including diabetes mellitus, lower urinary tract disease such as cystitis, joint stress that aggravates osteoarthritis, non-allergic skin conditions, and hepatic lipidosis, a condition in which fat builds up in the liver. It can also bring complications such as higher anaesthetic risk, weaker immune function, difficult births, and breathing problems (sometimes called Pickwickian syndrome), along with reduced stamina and exercise tolerance generally.

What drives weight gain

Weight gain happens when a cat takes in more calories than it burns over a sustained period, a positive energy balance, with the surplus stored as fat. The body normally regulates intake to match use, holding condition around a natural “set point”, but several factors can shift that set point toward weight gain.

Purebred cats tend to gain weight less readily than moggies. Neutering slows the metabolic rate by around 20 per cent, meaning neutered cats need less food than intact ones to hold a stable weight, and they also tend to roam less, cutting activity further. Activity levels generally play a large role: cats with less opportunity to move about are at greater risk than active ones.

Age matters too. Cats under two are less prone to being overweight, cats between two and ten need fewer calories and are more likely to gain, while cats over ten, the senior and geriatric group, tend if anything to be underweight.

Highly palatable, energy-dense food encourages overeating, especially when left out freely or used generously as treats. Certain medications can also contribute, either by boosting appetite or slowing metabolism, corticosteroids such as prednisolone, along with drugs like amitriptyline and cyproheptadine, are commonly implicated.

Treating obesity

Rapid weight loss is dangerous in cats, it can trigger hepatic lipidosis, a potentially fatal liver disease caused by fat accumulating during a period of fasting-driven metabolic change. A slow, steady reduction is the safer route, and a severely overweight cat may need up to a year to reach a healthy condition. A vet can design a weight loss plan combining diet, exercise and regular monitoring, since it’s genuinely difficult to notice gradual weight loss in a cat you see daily, regular weigh-ins help confirm the pace is right.

Cats are obligate carnivores, unlike dogs or humans, they need meat to survive, and their natural prey-based diet is naturally high in protein and low in carbohydrate. Veterinary weight-loss diets mirror this, being high in protein and low in both fat and carbohydrate, which helps cats lose fat while holding on to lean muscle mass.

Alongside diet, exercise can be encouraged through more active play, or simply getting a cat moving around the house more, using a harness for stair walks, or relocating feeding bowls to encourage movement.

Puzzle feeders are another useful tool, shown to support both physical activity and emotional wellbeing.

Keeping weight stable long term

Once a cat reaches its target weight, switching to a “light” or reduced-calorie food designed for less active cats can help maintain it. Just as gradual weight loss is hard to spot day to day, so is the early creep of weight regain, which is why ongoing weight checks matter even after the target has been reached.

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