City Animal Control Services is offering Melvin for adoption, along with 20-pound Marvin, who also was rescued from the home.
Dr. Marilyn Gotbeter, the agency's chief veterinarian, tells the San Antonio Express-News the cats "were cruelly confined, didn't have enough room to roam around and had no form of exercise or activity."
She says the animals gained weight from lack of exercise until becoming too fat to exercise. Melvin and Marvin worked out with doctors but quickly grew exhausted despite barely moving. In Gotbeter's words, "They basically pass out."
The vet says the cats are shy but sweet, and recovery is possible with a caring owner.