You are 12 and you weigh 142 you are going to try to only eat dinner for a week and see what happens?

Firstly, you may or may not be overweight depending on your height, bone density, and even nationality. Get your doctor to advise you.

While you may lose some weight, going without food for a long time changes something in your body that means you will put on much more weight more easily. Because your body thinks you are starving, it tries to store will lose a lot of muscle too. Eating in the way you described is not good for you at all. Try a better way of eating that produces real results by dealing with the underlying cause. Learn about low- GI eating. This isn't another diet, but a sensible approach to eating. Check the web link to the left for details.