I am 16, 1 m 69 and I am 80 kg. I just had my exams which is an important part of my education. So during that time I put on 15 kg. And when my exams were over, I tried joining Aerobics classes, but I was not allowed to  go outside the house since there was renovation works going on and someone needed to stay at home while my parents were working. And because of that I eat a lot of junk food. Now that school has resumed, with all those afternoon classes, tuition and homework, I don't have time to practice a sport outside. I need to lose 20 Kg and I need to lose them within the next 6 months. what do you suggest me to do? I mean something I can do everyday, irrespective of the weather? and what do you suggest me on my nutrition?