I need to flatten my chest, so should I increase cardio and cut out weight training?

If your goal is to lose muscle, you simply need to lower your protein intake, increase your cardio, and stop training with weights. You'll lose the muscle ... it is called the use it/lose it syndrome.

However, if your chest is flabby, i.e. you can pinch more than a millimeter of skin, then that thickness is fat. Your best bet is to continue to develop the chest muscles through lower rep-range resistance training, because those muscles will help you burn calories and raise your metabolism. Combine this with cardio and proper nutrition, and you will eventually lose the fat to define your chest.

Also, we all watch what we eat, or we wouldn't be very successful with reaching our mouths. The question is .. what do you eat? What's a sample menu?