DH and I went away for the weekend. Neighbor said he'd feed our three cats Sat and Sun. Sounds easy, just give them dry food in the 3 dishes provided each morning...
Came home to find my "little" cat had gained close to 1/2lb and has a huge belly! She should probably be in the 8lb range for her size, now she's closing in on 10lb! Apparently, neighbor does not understand that filling the bowls to overflowing proportions is not correct This particular cat does not/can not self regulate eating, she'll eat just because it's there. She also has a senstive GI tract with possible IBS, of course she now has a flare up from the massive quantity of food she consumed in 48 hours... Neighbor has been informed of what an appopropriate amount of food is.
So now I have a fat cat. It's winter, she will go outdoors, but not for long. How do I get her to slim down? The other 2 aren't bad, better at limiting themselves, though the other female has chunked out this winter too. Cat #2 is pretty good about losing the winter baggage come spring/summer on her own. I've got them on the Purina Pro Plan Vibrant Maturity as it's got the most fiber for the glutton/IBS cat and the other two are over 8 years. Usual serving is ~1/2cup 1x/day.
As an indoor exercise, see if they will run for their food. A friend slimmed down her obese cat by throwing its' food one piece at a time down the hall. Cat would run down & get the food then run back for another piece. She said it only took 3 times for the cat to figure out the drill & it lost about 3 lbs that way over a winter.
My chunkybutt has slimmed down very well since being switched to a canned-only diet. He was overweight and did not lose weight even on a lower-calorie dry. He's slimmed down nicely on the wet, and there are many other benefits of feeding a wet diet. Canned food is filling, but less calorie-dense than dry (and better for overall health). Ideally, look for canned with less than 10% carbs (so pate varieties, no gravy). This will also help avoid diabetes (which sucks to have to deal with. ASk me how I know.) Wet food is a more ideal diet for cats than dry, and the cheapest wet is still better than the most expensive premium dry. If your IBD kitty cannot eat wet for some reason, there are lower carb dry foods as well, less ideal, but better than most dry.
Also, try controlled feedings 2-6 times a day (more smaller meals are better, but if you can't, two is ok). Some cats don't do free-feeding well.
This page has two charts that list the as fed percentage of calories from carbs of many foods. Some are on the "old" chart, others on the new. There is a dry food chart somewhere, I believe. These must be obtained from the company, as the "guaranteed analysis" does not give an accurate carb count.
Wet only diets are usually lacking in needed taurine
??? since when? if it's made to any current standard it has plenty of taurine.
cats will usually rapidly lose excess body fat if you cut the (very unneeded) carbs out of their diets.
cats shouldn't be fed dry food regardless of its "quality", the dryness of it causes physical problems. Most dry foods are also high in carbs which will increase your cat's chance of developing a variety of unpleasant diseases of middle age.
I have a cat like that. He was a stray and will just keep eating until there is no food in front of him. He literally ate himself sick when I left them with a continuous feeder and a cat sitter checking once a day the first time I went away after I got him. Let's just say that the cat sitter now comes twice a day, and has a lot more work to do when she is here, because of him. You're right in that measured, controlled feedings are the only way to prevent this.
I would question, though, whether your cat really did gain that much weight in that short a time, or whether she was just bloated or heavy with undigested food and water weight from the abrupt change in her diet. Give her a few days and weigh her again, you may see a downward shift in that weight without doing anything.
Am I reading correctly that you are only feeding once a day? If that is the case, you may want to try moving up to at least twice a day, more if possible. That would be better for your cat. Think of how they eat in the wild, many small meals, small critters, insects, as many times a day as they can catch them. If your feeding more closely approximates that, you may find your little girl has a more reasonable appetite, though, to be honest, it doesn't work, appetitewise, with my guy. It does help keep all the cat's weight in check better, however.
My cats get either wet or dry, fed three times a day. They get a high protein dry and wet food -- 1/8 of a cup dry food a feeding or 1/4 of a 5.5 ounce can wet. I would prefer to feed all wet, but I have two who just will not eat much wet food. Since they're old, 13 and 15, they get some dry to make sure that they are getting enough calories.