Our cat is not a Maine Coon, but got very fat. The vet had her on diet food, and she still got fatter. The trick was to get a timed automatic feeder. Before the feeder, she would convince each of the three of us in the house that she had not been fed, so she was often getting 3x the food she should have.
Oddly, not far from my rural northeast Alabama home and church is a place specializing in Maine Coon cats. It’s called the Backwoods Kennel and Cattery and it is, indeed, backwoods. My 15 year old house cat died a couple of weeks ago, and I’d dearly love either a ragdoll or a Scottish Fold to replace him, but both are too expensive. He was a stray kitten, so like Janis Joplin wanted the Lord to send her a Mercedes, I want Him to send me a new stray.
My little fattie is on a $40.00 bag of food from the vet. Her coat looks better than ever, but she just can’t stop gaining. She looks like a fur ball with legs.