im 16 years old and i weigh 246 lbs.. i know its crazy so please dont make fun of me. but i wanna start loosing weight.. my goal is to loose 70-85 lbs in the next 6 months. is that too much if it is what is the appropriate amount. also how can i prevent excess saggy skin.. and are there free online support groups for teen girls? and does anyone know a good diet plan?

It is possible within 6 months if you work hard and are dedicated. Overall it depends on your body type and health history. Here is what you do.
1. Don't count calories or worry about eating fat etc like others may say. Stick to science when it comes to fat lose, not hype.
2. Eat when hungry, eat until satisfied, and never to get full. Repeat, repeat, repeat.
3. Eat good natural foods, you need veggies, good proteins, good fats, and overall good nutrition.
4. Avoid all processed foods, all sodas, sweeteners of all kinds, soy products, and all refined foods and grains.
5. Follow a diet for your metabolism. Check out Dr. Mercola on the web ane his book on metabolism.
6. Drink good water 8-10 glasses a day
7. Exercise. Aerobic is good for your heart and to get things flowing but it won't help much for fat loss. If you aren't use to exercise, start walking daily.
8. Build muscle. Muscle will burn the fat. Do sit ups, pull ups, leg lifts, and crunches daily. Increase your intensity every week. Add different varieties about every ten days. You must keep challenging your muscles or you'll stagnant after a few weeks.
9. Find someone to help motivate and keep you going. A friend, a coach, a personal trainer.
10. keep track of your progress and don't give up.
11. Don't worry about the weight, its fat lose and health that should be your focus.
12. Keep a positive attitude.
This plan works and is based on science.

Use Sparkpeople.com It is a great web site. You can type in the food you eat and you work outs and it will tell you if you are on track for your goal. IN addition, if you type in your goal and they feel it is unrealistic they will not support it.
They give you a food plan and work out regimen. It is great and it is FREE!

No that is not crazy .......and no that is not too much. As long as you are sure that is a realistic goal for yourself. Maybe you should set your goal for 50 lbs....then when you loose that wieght ....go for next goal weight. That is what i did...that way every time i got to a new goal weight it made it easy for me to reach the next oneHave you figured out what your BMI is ( body mas index)....and how tall are you...with that information you will have a idea of what your idea weight should be. There is lots of online help for girls/women...try a high protein..low carb/sugar diet...you will burn fat...and increase muscle...Good luck ....I know you will get there.

I would aim for 2Ibs a week, aka 8 Ibs a month. You are aiming for too fast a loss and it is less likely to stay off with the diet you'd need to lose it so fast.
There is a lot of info online on healthy eating, it isn't that difficult .
Try and keep your fat intake below 40g a day, keep away from all junk food, but let yourself have a treat once a week maybe... on a Saturday.
Drink lots of water, tea, fruit tea, but no sugary soda.
Eat lots of vegetables and fruit, lean meat, fish, occasioanal egg or two.
No white bread, white pasta, white rice.
Stick to wholemeal bread, wholemeal pasta, brown rice.
Baked potato with a low calorie topping is a good meal.
Snack on dried fruit, fruit, rice cakes, low sugar cerial with skim milk, fat free yoghurt etc.
And try and get 30 mins at least of exercise, 5 times a week. Start with walking and work up to jogging or swimming, maybe cycling even?
Good luck, you will get there.