Increasing the number of meals you have and reducing the amount with each serving should also help increase your metabolism. I'm helping a friend now who is pretty overweight and the first thing I wanted him to accomplish before getting wrapped up in the gym is getting his diet down.
I'm not talking about hating what you eat either. If you are working out in the gym and breaking a sweat you're burning calories so you should be able to eat tasty foods "within reason". Start off with small changes, diet soda, whole wheat instead of white bread, oatmeal in the morning, apples for snacks. You'll have to make it a life change decision in order for you keep your gains/losses.