I would suggest going down to only ONE feeding a day. Cats tend to eat on their "own" time. It is okay to feed animals once a day in alot of cases. I know many would be shocked at that statement. When the dogs or cats are puppies or kittens they should be fed atleast twice to three times a day, then after 6 months to a year, cut down to ONCE a day.
It may take some adjusting, but I would put the food out either in the morning or in the evening. Whichever one they seem to eat the most. My dogs are nighttime eaters and the cat morning. Just leave the food out and let them eat at their own pace.
Don't let them eat for a set time and take the food up. This will encourage overeating at each feeding. That could be a cause for the overweightness. Metabolism works better when fed at a slow pace than eating all at once and stopping.
Avoid any can foods. They are the highest in calories. The type of cat you have may be prone to overweightness. I've seen cats that tend to be more obese than others for no apparent reason. Maybe the cat is also a mouse eater and gaining weight that way.
I would also try to include more things for the cat to exercise on. Put in a scratching post or give them some kind of toy that requires exercise. This may also help. I am already surprised the other cat hasn't helped in that area as well. Keeping a buddy around sometimes helps an animal lose weight. Hope this helps. Us "fat" cat owner's have got to stick together!