That cat didn't appear to be THAT much over weight. We have a cat at the shelter that was about 45 pounds when he first came. A volunteer got him down to just under 40 and now I think he is around 35. He was adopted then brought back (that's another LONG story).
My Taz weighed in at 21.5 lbs at his heaviest and he could still jump up on counters and in the windows.

But yes, it is very sad when the owners do not realize what is going on. They just want to make their pet happy and feeding them is one way to do that. Oh wait.........that's my problem too with myself!