Keano, from Plymouth, England, UK, was so overweight at 101.4 pounds, he could not roll over on his back before joining the People's Dispensary for Sick Animals (PDSA) scheme.
Five obese dogs and one cat completed PDSA's 100-day diet and fitness program, devised by vets.
The charity said canine obesity rose by 9% in the last year, which can cause potentially fatal conditions.
New shelter data casts doubt on whether the pet population and pet ownership are truly growing.
While the pandemic caused unprecedented suffering worldwide in 2020, the disruptions to dogs, cats and other pets adoption numbers may normalize in 2021.