Seven-year-old Jack was out of breath and overweight.
The super-sized Spaniel was so big - he could barely move - when Mac and Rose Welch adopted him.
"He couldn't close his legs, he couldn't close his legs at all, they were that wide apart," says owner Mac.
So they signed up their dog who they nicknamed 'Jumbo Jack' for Britain's pet fit club.
With more than a third of dogs overweight or obese in Britain the group is helping pets transform their bodies as part of a six month fitness program.
Doctors say just like people, obese pets are more likely to have heart problems, diabetes and other complications.
Veterinarian Elaine Pendelbury says you should be able to feel the animals ribs through their skin.
"The ideal shape is to have the waist coming up like this, a svelt appearance."
She says one of the biggest mistakes people make is over feeding their pets.
"It's ideal if you are a couch potato because it's like: one biscuit for me a biscuit for the dog, that kind of thing but when you think about it the calorific requirement for the dog is very much smaller than ours."
Vets say one human treat alone can give a cat or dog a quarter of the calories it needs in a whole day.
"Unbelievable - 15 inches - wow!"
Jack's measurements and weight are taken each month.
Ten months after starting the fitness plan he has lost nearly half his body weight.
"Well done - good boy."
He was even crowned champion of the program's diet competition.