its not that hard to loose 5 pounds. all you need to do is crunches. not sit up but crunches. you lay down like you are going to do a sit up. you just use you upper abs you lift your upper body up 2 inches or so.
play sports, exercise ok this is what i doi do 50 pushups, situps, leg lifts, and 50 jumping jacks after i wake up and before i go to sleep. and what i do to gain more muscle is eat a lot of peanut butter or peanuts, chicken, and oatmeal then i run about an hour later to get the carbs off. i hope this helps o yeah im 13 too so it should work for you