Is it harder for a teenager to looks weight compared to a adult?

I have been trying to loose weight lately. I am 16, 210/11 pounds and 5'10. I have gone to the gym for about a month and half and I did not lose one pound, but I have noticed a stamina gain and muscular buildup as well as my keg shrinking. I used to attend the gym regularly 3 times a day, but now not so much (usually play basketball for 3-5 hours).My parents want me to lose weight and be in the 160-170lb. range, they want me to achieve my goal by the end of the summer. Is this possible? I have seen somewhere that a average teenager would have to work 3x harder then an adult to lose weight, is this true? And should I attend the gym daily to see results?