Originally Answered: are there any supplements that can get rid of my body fat?
First of all, no disrespect intended to earlier contributions, but the BMI index is crap. It can indicate that someone (like myself) is obese when they have 10 percent body fat and work out 7 days a week, while at the same time someone who has a higher than average body fat percentage can be considered to have a "normal" BMI. In the bodybuilding community, this body type this body type is commonly referred to as "skinny fat". I know- not pretty, but true.
So - to answer your question... there's no "quick fix". Getting your BF below 11% from 20% is gonna take a lot of dedication and hard work. Especially if you're trying to maintain or even build muscle while doing it.
Here are some tips:
1) Cardio EVERY day. Lifting weights does build muscle, and more muscle burns more fat, but lifting alone will not get you under 11% bodyfat- especially not over the course of the summer. I suggest running- A LOT! In addition to your cardio routine, you'll also want to do resistance training several times a week. Just be sure not to work the same muscle groups without at least a day to let them rest and heal between. This means either changing up your targeted muscle groups from day to day, or just doing a full circuit and resting (not lifting) every other day.
2) Diet is EVERYTHING. Fit bodies are built in the kitchen as well as the gym. If you're trying to drop a lot of fat, but maintain or build muscle, stay away from ketogenic diets (low carb, no carb). You need carbs for muscle growth. Don't go carb crazy though. You're not going to lose fat eating over 200g a day or carbs unless you're superman. Better to keep it around 100g. Also- you need to have some healthy fats in your diet to prevent muscle loss. Flaxseed oil or Fish Oil are good for this. About 10g per day. Most importantly- you need protein. A LOT of protein. About 1 to 1.5g of protein per pound of DESIRED body weight. So- if you're looking to maintain your size or get bigger while trying to get lean, you need to consume 160-210g per of protein. Avoid eating carbs and fats together in the same meal, or at least within 2 hours of each other. Protein and carbs or protein and (healthy) fats, but NEVER fats and carbs.
3) Supplements: As mentioned above, some of the basics will be flaxseed or fish oil and a protein supplement. I personally recommend Pro Complex. Add your flaxseed right to the shake when you make it. Other good supplements that will help your gains are Nitric Oxide and Creatine. Be careful with the creatine though. Some of them tend to make you retain water and will mask your fat loss results. Try to stick with one that's designed not to do this, like CE2 Hi-Def by MRI labs. You may also want to include Terris-Tribulus which is an herbal testosterone booster, but I don't know if that's something you want or need when you're 15. :) Oh- and finally, make sure you're drinking a lot of water and taking a good ol' multivitamin every day.
Sadly- supplements aren't cheap. You can do without them though and still get the same results, it just may take longer. It's also kind of tough to take in that much protein the old fashioned way without taking in a lot of fat. After a few weeks you'll never want to see another chicken breast!