Owners across the UK are being encouraged to help their pets stay healthy as a veterinary charity launches its Pet Fit Club competition.

A PDSA report last year indicated "deadly diets" are being fed to 18 million of the country's pets, with poor food choices, combined with a lack of exercise, increasing the risk of preventable conditions such as diabetes, heart disease and arthritis.

The charity has revealed a list of 21 overweight pets – 13 dogs, five cats and three rabbits – who will compete in the annual slimming contest. Bullmastiff Mizzy is the largest ever participant and at 11st 4lbs is 60 per cent over her ideal weight.

PDSA senior veterinary surgeon Elaine Pendlebury said the owners concerned had taken an important step towards a healthier future, which will reduce the likelihood of early death caused by obesity-related issues.

"Obesity is one of the biggest welfare issues affecting pets in the UK today – and it is entirely preventable. Sadly, it also means daily misery for millions of pets who are feeling the strain from carrying too much weight," she said. "The good news is that it's never too late to make a positive change to improve a pet's quality of life."

Jan Mitchell, owner of Norwegian Forest cat Ulric, explained her pet would habitually eat his own cat food and then his sister Ulla's, prompting Ms Mitchell to feed Ulla on the worktop as Ulric cannot jump up to it. At 2st, he is more than double his ideal weight and is the biggest cat ever to take part.

PDSA has been running the competition for nearly ten years and says participants' lives have been saved by the weight loss. This year's contestants will embark on a six-month diet and exercise programme, with vets and nurses from the organisation coaching the pets' owners along the way.

Written by: Hannah