I've tried cutting Millie down over the years and she's not as big as she was. But sometimes when I say "No!" she glares at me and goes out. When she comes back she is as fat as barrel! It's definitely not wildlife, I think she goes on a raid round various cat flaps lol!
I've actually never tried cutting Alf's eating back. He's on the chubby side, I can't deny that but he's a big breed and vets who know the breed says he's a little overweight but that's all. Harvey is actually underweight so that doesn't help any.
And Alf loves his food. If I go by the recommendation on the packs and how much he weighs he doesn't over eat. He's not as heavy as he was. But he's done that himself.