I've had my cat Cocoa Kitty on a diet for quite a while. The vet said he was too heavy and it would affect how long he would live, so I HAD to put him on a diet. He sometimes gets cranky when he's hungry and is more likely to give a little bite. Now I buy the pet grass at the petstore so he can at least "have a salad" when he's hungry. Then he was less cranky and still slimmed down. He's nearly at the right weight now....now I only have to work on slimming myself down!! I am really attached to the boy and he's very well behaved and sweet most of the time, so I really wanted him to be healthy and stay with me for a long time.
Try providing the cat grass and see if your cat is less cranky.