My Italian grandma was the worst with this–my parents would drop us off there for the day along with our miniature poodle, and that dog would spend the next eight hours straight stuffing her face. “Look at her,” my grandma would berate my mother as the poodle waddled slowly over and collapsed panting on the ground, “she’s starving. She ate an entire plate of meatballs today, she was so hungry. You don’t feed her.” And then she’d give her another pierogi.
I was shadowing at the vet’s once when I was in high school and saw surgery on a cocker spaniel so obese that the vet was pulling out globules of fat and setting them on the table to get at the relevant bits. My older mini dachshund was 21.5 lbs when I got her–her belly almost dragged on the ground.
At least in Obie’s case, it seems that his owners had some issues with dementia and kept thinking they hadn’t fed him. That happened with my younger dachshund, whose owner’s mother had dementia and kept giving him cans of cat food all day.