15 huh --- then you prob. shouldn't start taking supplements this early. I know being 15 is hard also to keep a clean diet.
Do you go to the gym? If not, it may be a great thing to go for a daily walk. Do things that use your muscles. If you think about it a lot, it may come easier for you to do. Do you drink a lot of POP? If so, switch to DIET pop....actually switch to drinking a lot of water. I am trying to think of easy ways - or little things to do daily that would help. Really, don't start supplements at such an early age - you will find yourself on them more than you should be. Just limit the food intake..... example: if you must eat pizza, try having just 1 or 2 slices -- try to eat baked chicken instead of fried ----
Try not to put salt on foods.... It is hard, but once you start with little changes, you will find yourself losing weight........
Do you live at home? If so...... Honestly, Vacuum, Clean -- you will find you work up a sweat very easily (and you will get brownie points from parents)