Cooper, a 30-pound Pomeranian-Carlin pinscher cross, struggles to walk and to breathe, and his immune system is depleted. (CBC)

The recent arrival of several morbidly obese dogs at an Ontario branch of the Humane Society has prompted a public warning that keeping your pet too plump can constitute animal abuse.

Staff at the Humane Society in Arnprior, Ont., have reported receiving three morbidly obese dogs in the past few months.

In some cases, the animals are so overweight, they're suffering serious health complications.

One example is Cooper, a three-year-old Pomeranian-Carlin pinscher cross that should weigh about 10 pounds. Instead, he weighs in at a whopping 30 pounds.

Cooper was picked up as a stray a couple of weeks ago, presumably abandoned by his past owner.

Valerie Hemphill, an agent investigator with the Ontario SPCA, said she would have laid charges against the owner if she had found him or her.

Diabetes on the rise

"If you want to put this in human terms, you look at a 100-pound person who's actually weighing 300 pounds," said Hemphill. "That's morbid obesity."

While the "pudgy-puppy" look might be considered kind of cute, the consequences are serious: Cooper struggles to walk and to breathe, and his immune system is depleted.

A 25-pound Pomeranian was also dropped off on Thursday.

"This is one example of what seems to be a growing problem," said Hemphill.

As people have grown more obese, so too have their pets. In fact, veterinarians in Canada and the United States are reporting a notable increase in cases of Type 1 and Type 2 diabetes in both dogs and cats.

1 year to get Cooper fit

"If you're feeding a lot of fat foods, like pieces of pizza and bacon, and a little bit of this and a little bit of that, it all adds up," said Hemphill.

"Yeah, he's sitting up begging, and he's so cute when he begs, but it doesn't mean you have to give it to him."

In fact, Hemphill warns that owners who spoil their pets in this way could be doing serious harm and could even face criminal charges.

"This actually is abuse … this is cruelty. This [Pomeranian] struggles to walk, he struggles to breath, he could potentially have many ailments."

Cooper, meanwhile, has been picked up by a foster family.

The dog is now on a strict regimen of exercise and high-fibre foods, and he has lost two pounds in just the past week.

But it will likely take about a year to get Cooper slimmed down to a healthy weight.