Hi,
Thank you for consulting with Health Care Magic. I understand your concern, and i hope my suggestions will help with your problem.
Considering your age, ideal weight should be around 35-40 kg or 75-80 pounds. If your weight exceeds this then taking few measures to cut down the extra pounds is a good step. You need not be so worried about
diabetes unless it runs in your family.
Swimming is a good sport you have chosen to lose weight, drinking water (not necessarily
cold) 4-5 litres a day proves helpfull too.
Cut down on all junk food and aerated drinks. Exercise well and eat healthy.
Join some kind of sports in school which will help you burn calories.
Follow all this for 4-6 months and i am sure it should help you reduce weight.
Meanwhile consult a dietician and get a detailed diet menu suitable to you.
Hope this helps.
Write back to me for further assistance.