The US pooch, who was overfed by his doting elderly owners, weighs an incredible 35kg.

When a relative of the former owners asked for help in getting Obie to slim down, Portland resident and dog-lover Nora Vanatta stepped in.

“Ageing owners with failing health were simply loving him with food,” Ms Vanatta explains on a Facebook page dedicated to helping the dog.

“They just couldn't say no to those big brown eyes.”

Ms Vanatta, who is a vet and has a degree in animal science, says she didn’t know what to expect when she first heard about Obie, but knew exactly what to do when she saw him.

He was placed on a special diet to lose 18 kilos - about half his body weight – and once he slims down, he can start swim therapy and go on the treadmill.

“I feel tremendously blessed to be involved in his rehabilitation and I am amazed at the outpouring of love and support that I have received,” Ms Vanatta says.

Despite being overweight, a blood test confirmed that the dog is in relatively good health. He will, however, need to have dental work and may need to have his excess skin surgically removed.

"He is extremely sweet and loving and is a joy to work with," Ms Vanatta says.

“My hope is that he can be an inspiration to any person or animal trying to lose weight.

"It is so important to introduce pups and kids to a healthy lifestyle."