Here’s a paradox: the biggest cause of suffering in pet dogs may be  people who believe that they love their pets the most. What am I talking about? Overfeeding and its consequence: obesity.

Over a third of dogs in the UK (2.9million) are overweight or obese while 25 per cent of cats (3 million) suffer the same problem. These animals have a serious risk of developing diabetes, heart disease and arthritis, and have a lower life expectancy than pets with a healthy weight.

Arthritis is probably the most common issue that causes physical suffering. As a vet, whenever I treat an older dog for sore joints, I write out a check list of the treatment plan. And the top of the list, in nearly every case, is “weight loss”. For many animals, this is more effective than any medication.

The people at Battersea Dogs and Cats Home will be discussing this problem in tonight’s episode of Paul O’Grady: For The Love of Dogs on ITV1 at 8pm. Prevention of obesity seems simple in theory, but for some reason, many pet owners find it difficult. Again, part of the problem may be that we see pets like little humans, and we feed them accordingly.

The Battersea team have put together some simple tips that may help owners understand how to keep their pets slim and trim.

The first aspect is to work out the amount that a pet needs to eat: this depends on its breed, age and size, but as a rough indication, a small dog only needs about 350 calories a day while for a cat, it’s around 280 calories. So a slice of toast is equal to a third of the dog’s daily calories, equivalent to a human eating half a loaf of white bread. Other useful comparisons include a 3cm cube of cheese (equal to a whole cup of molten fondue cheese), one custard cream (half a pack of custard creams), and half a tin of tuna (a large cod n’ chips from the local chippie).

The second tip is to stick to a standard diet, without extras. It’s a common misconception that dogs and cats get bored with their food. When pets turn their noses up at their dinner, it’s often because they aren’t hungry rather than because they don’t like it: they will often still eat interesting nibbles if offered. It’s similar to the way that we humans will often manage dessert at the end of a meal, even if we’re feeling comfortably full. This is a common cause of weight gain in pets, just as it is in humans.

Third, if you’re worried about your pet’s weight, consult your vet. There are medical reasons for weight gain that may need to be ruled out, and a regular (free) weigh in on your vet’s electronic scales is the best way to monitor your pet’s body condition. It’s difficult to assess this by just looking, especially when you see your pet every day, because weight gain happens so gradually.

Pets don’t get fat because they choose to eat too much: it’s because their owners choose to feed them so much.

If you have an obese pet, there’s no dodging it: it’s your fault. The situation can be remedied, so don’t despair. Take an action to do something about it today. Go on: pick up the phone, call your vet and arrange that all-important weigh-in.