Half of dogs face an early death amid a growing obesity crisis

Vets warn that if current trends continue, then by 2013 half of all dogs in Britain could be overweight - putting them at risk of diabetes, heart disease, arthritis and other illnesses.

But part of the problem is that people persist in seeing their portly pets as "big" and "cuddly" and are blind to the serious health issues caused by obesity.

PDSA senior veterinary surgeon Sean Wensley said: "We know from our work with pet owners that many view an overweight pet as cute and cuddly. What they don't see is the threat that obesity poses to their beloved animals' health and lifespan.

"Overweight pets are less mobile, less willing to play and more likely to develop a number of serious health conditions.

"Ultimately, owners control their pet's diet and exercise. The good news is it's never too late to achieve positive change."

Over the past four years, the PDSA has assessed the weight and general health of nearly 30,000 dogs across the UK and it has seen the percentage of overweight dogs nationwide rise from about one in five (21 per cent) to more than one in three (35 per cent).

Scotland, the south-west of England and the Midlands are the areas with the highest percentage of overweight dogs. In Scotland, the proportion of dogs that are overweight has almost doubled in the past four years - from 19 per cent in 2006 to 37 per cent in 2009.

In a drive to cut animal obesity, the PDSA has launched an appeal to find the most overweight pets in the country to help them slim down. Selected pets will be put on a free six-month diet and fitness programme overseen by PDSA vets and nurses.

Last year Tara, a black labrador from West Lothian, was one of the pets chosen for special treatment. At 42kg, Tara was 66 per cent overweight - but today she weighs a healthier 35 kg. Owner Linda Smith said: "Tara was dubious about her new diet at first, but soon got used to it. The first few weeks she kept sitting by the kitchen cupboard, where her treats used to be kept, whining.

"She has put on a bit of weight since the competition finished, but I'm back to following the vet's advice and am determined to get her back on track with her weight-loss. Taking part in the competition was really helpful and I'd encourage anyone with an overweight pet to enter."

Dr Alex German, a leading animal obesity expert, is backing the appeal and said: "PDSA is doing great work in highlighting this important animal welfare issue via its slimming competition. It's vital that owners recognise their pet's weight problem, seek veterinary advice and do something about it.

"Through its competition, the PDSA is putting the spotlight on the pet obesity epidemic and offering practical help to improve the quality of life of the participating pets.

"Previous years finalists have achieved fantastic results and similar success this year will once again provide real-life demonstrations to pet-owners of what can be achieved with commitment and veterinary assistance."

Weighty issue

• Recognise the problem. In a recent survey, 71 per cent of owners of overweight pets did not realise there was a problem.

• Start young. Good habits begin young and fat puppies and kittens are much more likely to develop weight problems when older.

• Take care with treats. Giving a pet a treat can be an important part of training. But if a dog has been given lots of treats, then it is important to cut back on meal sizes.

• Develop an exercise plan. Getting lots of walkies is a great way for owners and pets to stay fit. But it is important not to overdo the exercise for a fat pet - so build up slowly.

• Talk to the vet. Often pet owners are unaware of what the correct body weight and shape is for their pet. A vet can offer advice your pet's ideal weight.