One fat cat and one skinny cat?

Maybe you could feed them seperately? Put one in a bathroom and one in a kitchen or something & That way you could cut Cletus' portions, and add to Kate's. Or, maybe you could feed Kate 3 times a day until she puts a little more weight on?

Also, are you free feeding?

exercise for the overweight one....like us diet alone isn't going to solve our weight problems (darn it) (now trying to type around my foster cat who keeps trying to get the cursor).
Our of my 4 cats two are at a good weight, 2 are a bit chubby. The 2 thinner ones are far more active than the 2 larger ones. I try to play wand toy every night with the overweight 2...one barely moves (she's 10).
Get a laser toy or something interactive and get some exercise time in.
When I was at the vets one day a lady was there with her 2 very overweight cats talking about diet and low-calorie foods. The vet told her she could feed them light foods forever and they simply won't lose weight until they get moving.

Also, are you free feeding?

Not really free feeding, but they do get the amount of kibble for their size that is recommended on the bag. They usually take all day to eat it. I think I may have to try sneaking Kate an extra meal in the evening. That darn wet cat food is so pricey, that I think I may cook her some chicken to supplement the dry food.

I'll try more exercise for Cletus, too. He is already quite active. He likes to taunt the dogs, so he gets chased quite a bit [] Unfortunately, the dogs like to join in when we play with him. He used to play fetch before we got a new dog. Now Lucy usually bowls him over to get his tinsel ball so he hasn't played fetch much lately.

Free feeding doesnt work for a lot of multi cat homes, for the same reason it doesnt work with multiple dogs. You dont really have control over who eats what. I'd start feeding them on a schedule and cutting back on the overweight cats kibble.
 
Also, alot of excersise. For the skinny one a few meals of canned a week and a set amount of kibble should do the trick. Canned wont be that expensive. I know one can of cat food lasts for about 2-3 meals with my girl.

The reason I was asking about free feeding is because the skinny cat might not be finishing her food and maybe the chubby cat is doing it for her. I think you have gotten good suggestions though. My cat gets fed until he stops eating, and then I take his bowl away. (Not because he is becoming overweight, but because the puppy has acquired a taste for cat food, haha) The kitty eats A LOT but he is still small because of his constant playing with the puppy.

How old is the older cat?  Most (indoor) cats will look like stereotypical little, round old ladies as they hedge into the 'senior' stage, which can be quite a few years depending on the cat.  Just imagine a ruffly apron, cap, and bifocals on your kitty if you see what I mean.  [&:]  It isn't unhealthy as long as she doesn't cross the line from plump and happy to round and unwieldy. 

Until recently we had three cats in my home:  a six month old kitten, a four year old middle-aged Miss, and an older ten or eleven year old Matriarch.  You have to really keep an eye on those guys to make sure everyone is getting what they need!  In the end, I found that structure in feeding and play is what worked best.  They were given almost a full day's portion in the morning when I got up, and at night, when I got home from work, they got the tiny quarter portion left.  This resolved the differences in eating patterns.  The kitten (Cicero) gobbled a pile of her food right away and zipped off to play.  The 4 year old (Fiji) is a Lady and would eat a dainty breakfast before going off to wash.  The old maid (Church) would wait to eat last because she didn't want to deal with sassy young whipper-snappers.  At night they would each come eat a little bit of the second portion if they wanted it at some point, and by morning it was gone.

At FIRST, for perhaps a few days, you better believe that somebody was going hungry.  But as soon as they realised the routine, they wised up and began pacing themselves.  It happened faster than I expected it too, actually.  Now nobody is greedy because they know exactly when they will eat every day, and that it is reliable.  I really have to stress that it must be the SAME TIME every morning.  Um....better make sure it is a time you won't mind being woken up at on weekends, because those cats will become the most accurate alarm clocks EVER.  []

No method is perfect and works for every household and animal, but this is one that has worked through the come and go of many fosters, for many years.  Make sure they have toys, scratching posts, and a indoor cat tree to climb up and play on.  They will exercise each other when you are not there, and you should take a little time for them as often as possible.  Play with them, show them how the toys work, make the toys more fun.  Cats are independent and that usually means, with a smart mommy or daddy to give them a hint, they will work out the rest.

Thanks for the tips! I'm going to start picking up their bowls after breakfast. I already have the furry alarm clocks. They all gather around my bed when the alarm goes off and I usually have to push one or two dogs or cats out of the way just to hit the snooze. On weekends, if I try to sleep in, they all line up beside the bed and I have eight eyeballs boring into me. If that doesn't work, Cletus, the younger fat cat, will start biting.

It is the 13 year old, less active cat that is underweight, and now that I think about it it all started this spring when we got our newest dog. Kate is one of those really fussy cats that gets upset if I rearrange the furniture. She would hide out under the kids' beds all day after we got Lucy and probably wasn't eating enough. She is now finally starting to get comfortable around Lucy so hopefully, splitting their feedings will help keep Cletus from porking out while Kate is busy being fussy. She has been comfortable enough to come out and beg at suppertime just the last couple weeks, so she gets some supplementation that way. Since the dogs have to quietly lay in their designated spots to get scraps at mealtimes, and Kate gets to sit right next to me, the dogs now know where they rank on the family totem pole! []