Good weight loss/general health diet for a nearly 16 year old?

I'm male, 15, 5'10" and around 10 stone but I don't know for sure. I have a bit of flab that I want to get rid of around my belly and hips so that I can start working on bulking up muscle, so I figured a change of diet was in order. I already drink only water and most days I have fried eggs for supper, so what dietary changes could I make most specifically to breakfast and lunch? I do a fair bit of cardio exercise too