Dennis is a miniature dachshund but there was nothing mini about him the first time Brooke Burton met the dog. It was 56 pounds, equivalent to around four or five mini dachshunds, and could walk no more than a few steps before running out of breath. Now, Dennis has lost 44 pounds and has become practically a new dog when all the weight came off.

Burton adopted Dennis from a relative who made a habit of feeding the dog human food. Particularly, Dennis had a steady diet of pizza and White Castle burgers, among other things. But when the dog started packing on the pounds, growing a belly, as anyone on a diet of pizza and burgers would, his old owner didn't pay attention.

Dennis started living with Burton in 2013 after she convinced the dog's owner to give him up. She recounts how emotional she was when she first saw Dennis. She wasn't even sure what kind of dog he was because he was so big.

To help the dog drop all those extra pounds, Burton put Dennis on a dry dog food diet. No more human food for the mini dachshund! Aside from saying goodbye to pizzas and burgers, Dennis also started going on a lot of walks. Eating better and engaging in regular physical activity is what helped the dog drop all that extra weight, slimming down to 12 pounds, just the right weight for a dog of his breed.

Unfortunately, losing weight left Dennis and Burton with another problem: the dog's saggy skin. He was so big previously that when Dennis lost weight, he had so much excess skin he was tripping over his own folds and getting infections.

To take care of this problem, Dennis underwent three surgeries at the Ohio State University Veterinary Medical Center. With excess skin out of the way, the dog is now able to chase squirrels without trouble in their backyard, play fetch with Burton and boss around his three other rescue dog siblings.

"In the beginning, you could tell he was very depressed, that he really didn't feel good at all. After he lost weight ... he's into everything, he wants to play with everybody," said Burton.

Overweight pets, like humans, can suffer from a number of health problems like respiratory disease, insulin resistance, high blood pressure, heart disease, osteoarthritis, knee injury and cancer, reducing their life expectancy by up to 2.5 years.