Humans and animals are the same: everyone loses weight through diet and moving. Feeding a cat three times a day sounds excessive. You should do what your vet recommends, my two eat 1/4 cup dry in the morning and 1/4 wet in the evening...they are a bit small though. I look into a higher quality cat food if you are feeding something like Whiskers or another cheap brand like that. Think of cheap pet food as giving your cat a bowl of fast food... and we all know what fast food would do to our weight and bodies if that's all we ate. Buy a few inexpensive toys and play with the cat. Like a feather teaser, balls, laser, etc. That will get him moving and will give you bonding time with the cat. Some cats eat everything until they are sick and some pick at their food. Don't be worried if you are feeding him and he's still acting hungry.