In fact, he was so out of shape, shelter staff thought he suffered from seizures because he panted so hard after what seemed his first real walk.
But it didn't stop Charlie from finding a foster home, thanks to the efforts of a rescue called Dumb Friends League. And the perennially open door - and hearts - of a local family.
Alaina Bupp and her husband agreed to foster Charlie for a month and keep an eye out for possible seizures.
Surprise, surprise. Charlie didn't have another so-called seizure.
And after a month of fostering him - and giving him the exercise he needed - Bupp decided Charlie should stay with them for the rest of his life.
"There was something about Charlie," Alaina Bupp tells The Dodo. "We both wanted to keep him. We both decided he was a permanent member of our family."
After doting on Charlie for a while, the Bupps decided it was time to return to the fostering world. They wanted to help more dogs like Charlie.
Their first opportunity was a tiny Chihuahua, a dog who was so severely underweight, he was cold all the time.
And that's where having a plus-size dog came in handy.
The Chihuahua realized that Charlie was more than just a love battery. He was 100 pounds of unconditional warmth.