On diets and cats-- I posted this elsewhere, and felt it deserved a mention here. Someone asked ways to get a fat cat to lose weight in a multi-cat household. This is most of the methods I have tried/had recommended to me to get Sassy fat cat to lose weight (and yes, she's been diagnosed with diabetes). Note: We have 4 cats, all rescues, and they all have issues.
1. Feed the cats on a schedule and only feed them as much as they need. Feed the fat one apart from the others, and feed her diet food in set portions. you can feed 3 or 4 times a day, in small portions to prevent binge/purge issues. (I have a skinny cat that does that). We free-feed and have a cat that will not eat while watched/skittish by nature. He would rather starve than try to be put on a schedule.
2. Segregate her in part of the house with the diet food, ideally with portion control. If this is unbearable, consider only segregating her at night/while you are at work, and picking up the main food dish while she is socializing with the rest of the family. This way you can continue to free feed the rest of the cats. We tried putting Fatso in the basement with a bowl of water at night. She clawed her way out. I am home all day, so shutting her up all day didn't go over well at all.
3. Put the food dish in different locations so she has to climb/hunt for it. Make her exercise to get her food. This is also fun for the other cats, unless you have one with mobility issues. This also helped keep the dogs out of the cat food. Unfortunately one of our cats has only one good eye and a badly set hindlimb, so jumping is ... interesting. I like this one best, because it is mental stimulation and breaks the monotony a little.
4. Put everyone on the diet food. Theoretically, the skinny cats will just eat more. Unfortunately, the fat cat ate more and the skinny cats got skinnier. One of the cats was having other health issues and could not afford to lose weight the last time we tried this.
5. What worked best for us- Sassy went from 17.8 pounds to 10 pounds- by living with another household for a year. They also had a fat cat, and I paid for the diet food for both cats and Sassy's regular vet care. It was clear that she was still Our Cat. But there were no competition/segration/portion control issues this way. We called it Fat Camp. This is a rather extreme solution and not usually practical.
When Sassy came home from Fat Camp, she slowly gained weight back and was diagnosed with her diabetes. She is now 14.3 pounds. She has never been energetic or interested in playing, so doing anything for her exercise is difficult. I like to pick her up and hold her 6 inches above the ground and she will squirm for all of 5 seconds before going completely limp. But that's more exercise than she got without my lifting her, and it's good exercise for my lazy bum too.