Can you resist the pleading eyes of a cat keen on the piece of ham you're just about to eat? I can't, and this is bad news for my cat Freddy. He is getting very fat.

More than 18 million of the UK's pets could have a premature death because of their diet, the vet charity PDSA warns. Owners like me, wanting to please their animals by giving them fast food, crisps and cakes end up doing them more harm than good.

Like people, animals can suffer from obesity-related conditions such as arthritis, diabetes and heart disease. Breathing difficulties made Phillip Howse take his mother's fat cat Jesse to the PDSA clinic in South London. He said the animal sounded "as if snoring when awake".

According to Howse, his elderly mother is too soft with her pet, which keeps meowing in the kitchen till it gets its treats. He tells his mother she "has to be cruel to be kind" if she wants to keep the cat for a long time.

But there's hope for poor Jesse. Last year, the charity chose 16 obese pets to try its six-month diet and fitness regime. In total, the pets lost a combined weight of 57kg. The slimming champion was a dog, Ruby. It went from 9.1kg to a healthier 6.2kg.

The way we treat our animals may be a reflection of the way we treat ourselves. According to the PDSA's Elaine Pendlebury, studies have suggested that overweight owners are twice as likely to feed their pets table scraps. And they end up with overweight animals.

Regular exercise is good for humans and pets. The charity's website suggests that dog owners run and play games like 'fetch' with their pets, but advises against throwing sticks as these might end up hurting the dog's mouth.

Cat owners should set time aside to play with their pets regularly and encourage them to 'work' for their meals, by using toys that release food when pushed around.

My own cat Freddy's diet and exercise plan starts on Monday and so does mine. Because it's not really the pet who opens the tin of biscuits. Both of us have to learn how to feel like "the cat that got the cream" - without really getting any cream.