If you want to know if your cat is overweight THIS is a site that has a diagram of cat shapes from thin to obese as a general guide.

I feed my kitties dry food 4 times a day. Some are allowed to eat until they walk away then I pick up the bowls, others have measured out food and when the bowl is empty I pick it up and guard the other bowls so they don't get more. I feed about 1 tbs of wet food in the morning only, mostly because Jack (and previously Dusty) require special medicine in the food and wet is the easiest way to give it. I give the wet to the others to keep them occupied so the one with the medicine can eat in peace.

A pet fountain really does help to get a cat to drink more water, which would help some with preventing UTI's.

Cutting back a bit on the food and feeding more often helps cats from feeling as hungry. More exercize helps. And you don't want them to loose too much weight too fast, a gradual reduction in food and more play time should get the results you and your vet want.

BTW: some cats are just prone to underbelly 'dingle-dangle'. I know several cats, and have a couple myself that have the 'dingle-dangle' and have NEVER been fat a day in their lives, seems to be genetic.