Dennis the dachshund is winning the battle of the bulge after a successful doggy diet.

Dennis lost 40 pounds after Brooke Burton adopted him from a relative who fed the dachshund burgers, pizza and more. A diet of dry dog food plus exercise helped slim Dennis down from a whopping 56 pounds to a slim 12 pounds.

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Read more from the Associated Press:

"In the beginning, you could tell he was very depressed, that he really didn't feel good  at all," Burton says. "He didn't have much of a personality. After he lost weight, this bossy little demanding man popped out. He's into everything, he wants to play with everybody."

Dennis lost so much weight that he started tripping over the folds of excess skin that were left over and getting infections. He has had three surgeries at the Ohio State University  Veterinary Medical Center to get rid of it.

Dr. Kathleen Ham, the veterinary surgeon who performed the operations , says Dennis' story is a good lesson for pet owners who might feed their animals too much.

"We have an expression: food is not love," Ham says. "Most of what your pet wants from you is affection and attention."

See a “before” photo of Dennis above, and check out his amazing transformation below.