How to diet cats like these

So, my mother tried putting her cats my little sister on diets. The vet said that they needed to be fed less can because of their weight the tar on their teeth. Well, she took away the can, it's been nearly a year now if not more, only 1 of her...

cats have lost weight, the others have gained. Since they've been taken off can they've been hunting more(a lot more). Killing eating rodents, birds, insects, anything smaller than them. They're getting pretty fat I'm getting a bit worried about my mothers sisters cats' health because they keep getting chubbier. So, my question is, how do you diet these cats who are determined to have their meat?

Hope this helps:
http://ezinearticles.com/?Homemade-Cat-Diet---Safe,-Healthy,-and-Deliciousid=1305371
http://ezinearticles.com/?A-Low-Sodium-Cat-Food-Diet-Can-Extend-Nine-Livesid=406857

Merry Christmas !!

not really
it's not what she's making them any more that's gettin gthem fat,
they're out hunting for prey are getting fat really.
It's a bit worrying

thanks, Merry Chistmas to you too