Around 17 of the lumpiest pets in the United Kingdom are going to compete in this year's annual slimming competition for pets called the Pet Fit Club. The event is mounted by the People's Dispensary for Sick Animals (PDSA), a veterinary charity.

Three of the contestants include Scotland's chunkiest dogs: Harley, a cocker spaniel, Kayla, a mastiff, and Bobby, a Labrador. These pets are at least three times bigger than their ideal weight, and their owners confessed that they can't resist it when their dogs beg for food, according to the Daily Record.

"He's spoilt and I feel guilty when I don't feed him a treat. I want him to lose weight for his health and happiness," said Harley's owner, Lisa Mitchell.

The PSDA believes that owners are largely responsible for why their dogs or cats are obese. However, it's not just pets with over-eager owners who are having weight problems.

Among the contestants, there's also a pug named Rolo from London who was "morbidly obese" even before he was adopted in 2013, according to London Evening Standard. "He has a habit of chasing people carrying shopping bags of food and has even been known to follow complete strangers into their home," said Lydia Ernstsons, his owner, according to The Telegraph.

Then there's Hooch, the Rottweiler who is the heaviest animal that has ever joined the contest, altough he has already slimmed down shortly after he was rescued. "Hooch was mistreated before, so he's a bit wary of strangers," said Leslie McCormack, his master, in the Standard report. "He used to eat five tins of dog food a day but I've cut him down to one."

These pets are guided by a program tailored for them by the PDSA in pet hospitals in Dundee, Edinburgh and Glasgow. The winner of the contest will be known by December. The prizes include a year's worth of healthy animal food supply and a holiday in a pet-friendly destination with its owner.

"With millions of pets receiving unhealthy treats such as crisps, cake and cheese as part of their daily diet, and millions more not getting enough exercise, it is clear that the serious issue of obesity in our pet nation is only going to get worse," said Nicola Martin, PDSA's head of pet health, Mirror reported.

"All the pets taking part in Pet Fit Club this year are taking the first step towards a longer, healthier life. Anyone concerned about their pets' weight should speak to their veterinary practice, who can offer the right advice and support."

The Pet Fit Club was launched 10 years ago and has helped 63 dogs, 26 cats and 6 rabbits slim down.