One of the most important things to do, when helping an obese cat reduce is
get rid of the kibble.
Kibble is empty calories, high carbohydrates (which cats don't need and cannot process) and dehydrating. And no cat ever got healthy on a "weight management" kibble, because those are generally even higher in carbs than other kibble.
Having said that to address the OP: Obese cats of unknown health status really should have a check up and lab work first to make sure they don't already have diabetes or other diseases that obesity can cause.
Also, as someone else mentioned, it is extremely important that the cat lose weight very slowly.No more than an ounce a week, or less. I recommend purchasing a baby scale and weighing weekly or every two weeks.
Feed small meals frequently. Add a little water to the meals. Feed canned pate products that are low in carbs. Fancy Feast classic is one. Depending on the weight of each cat, I would recommend you start with 6 ounces a day, per cat, split between four meals.
The division in time does not need to be even. They can still get their overnight fast (to help with motility and pyloric emptying) and the four meals can be fed during the day, at scheduling that is convenient to your day. Last meal at bedtime. Play some interactive Games with them first. Get them running and jumping and climbing.
First meal at breakfast, but don't feed as soon as you get up. Let them wait a little. Encourage a Game before you feed them.
Even if they don't seem much interested in playing yet, as they lose and start to feel better (both from the weight loss and getting rid of the kibble) they will start to be more intersted in playing.
Weight the cats on the day you start. Weigh them again in one week. If no weight loss, don't make any changes yet, wait a week and weigh again. If no loss again cut back a very small amount from the 6 ounce total. And proceed this way.
If there is weight loss already, and it is one ounce or less, continue with the 6 ounces and monitor. If the cat has lost more than an ounce, on 6 ounces a day, it's happening too fast, so increase the amount of food by an ounce.
Adding a little water helps slow the cat down from gobbling the food, and helps them feel fuller, and keeps them well hydrated.
The benefits of feeding more meals a day, is to keep the cat from getting too hungry, and to keep the cat from having sugar lows (which are caused by carbs in the diet) and to allow more flexibility, as you cut down on their quantity. Reducing each meal by a little bit, when you are feeding 4 meals a day, is easier on the cat, then making two meals a day smaller.
I recommend keeping a journal record. Weigh at the same time, in the same place, every week. Make not when you weigh, if the cat has recently peed or not. pee is heavy and can affect the accurate weight tracking.
Here's how to check carbs:
Cat Food Nutrition Calculator | Elizabeth C Scheyder
The number one way to help a cat reduce: Get rid of the kibble.