a good, cheap way to lose weight and get fit is taking up walking, progressing to jogging, then running. so for the first few weeks try a 30 minute walk (or as long as you want) everyday, then as your fitness improves try jogging half then walking half, for as long as you feel you can. the good thing about this is that its unlikely to get boring as you can vary your route, your speed and your length of time to give you some variety.
As far as eating goes, you should aim to gradually make small changes to your diet that will eventually add up to a complete change of lifestyle. for example, for the first few weeks try cutting out junk from your diet, then next increase the amount of water you drink, switch white bread for wholemeal, eat a healthy breakfast (eg. oatmeal, fruit, eggs) and snack on fruit and veggies.
hopefully this might work for you, i think its good that you're trying to make a positive change to your health at this age. its much easier to do this while you're young as your skin is more elastic and should shrink easily as you lose weight. plus, by making changes to your health and fitness at this age you'll be helping yourself to be a healthy adult, and maybe live longer. best of luck to you
ONe very good method for running is called the 60 second run. Its a progressive 10 week program and works like this.
Walk 2 minutes Run 1 minute and repeat this process 5 times. Thats 15 minutes. Do this 4 times a week alternate days. Then week 2 bring it up to 6 times then 10 times etc. When your up to 30 minutes go back to week one. But now run for 2 minutes walk for 1 minute. Repat 5 times. Then repeat again untill your up to 30 minutes and so on. Then start to run for 5 mins rest for one and just keeping up the gaps week by week untill you at the level you want. Perhaps you aim is to run 30 mins non stop 4 times a week. This program will bring you to that level.
This is a good method for anyone who wanst a safe and easy way into running. Its very gradual and will ensure that each workout is not too hard and will make you go back for more. Believe me using this method you could train up to marathon level. It's all aabout doing it slowly and having workouts where you feel engerzied afterwards not wiped out and hating it so much you end up quiting.
HEY!!!! did ya put on all that weight in 3 or 6 months???? If ya wanna keep you weight off permently, aim for 2 lbs a week. If you crash diet, and work out like crazy for 3 months, what are the chances of keeping that up for the est of your life?? NONE!!!! loosing weight and getting fit are about lifestyle changes, ones that you can keep forever, and keep you looking good for life.