How to stop exercising without gaining weight?

I plan to run intensely for the next two years of high school. When I go off to college, I plan to drop it immediately. I am worried that going from a high activity level to a non-existent activity level will result in massive weight gain.

Is there a weaning process? Gradual cut back? Every P.E. teacher I've had was fat because they had been so active as kids (and therefore were interested in the job), but upon the eve of their teaching job began gaining weight like crazy. These teachers were 50+ pounds overweight. If I train intensely, I worry I will wind up like them.

Why do you want to "drop it immediately" once you're at college? Running is a really great physical activity. Why give it up? Make it a lifestyle change instead of a weight-loss tactic, if that's why you're starting.

Why give it up completely?  You keep your heart healthy by running.  In any case, you are going to have to be eating A LOT more while you are running intensely for the next two years.  So, essentially, if you really want to stop running altogether, you are just going to have to cut back on the number of calories you are eating.  Plug your stats into this calculator:

http://www.phord.com/cc/

This will help you figure out how much to be eating while doing this intense running (if you don't want to lose weight, eat the calories under the BURN section.  If you want to lose weight, eat the calories under the EAT section).  In any case, once these two years are over, go back to this calculator and re-enter your stats...essentially you will have to change your activity level. 

If you don't overeat, you won't gain weight. 

Good luck!

I wouldnt drop it. 20 minutes of physical activity a day has been correlated to higher GPAs. Plus colleges always have the best gyms!

I wouldn't drop it completely.  If you're sick of it find something else.

You don't HAVE to exercise to not gain weight.  Of course exercise GOOD for you and I think EVERYONE should do it b/c our bodies were designed to move.  But the truth of it is you could lose weight or maintain through diet alone.  All you need is to eat what you burn or eat less than you burn.  

“The price to pay for quitting exercise is higher than expected, and this price may be an important factor in the obesity epidemic affecting Americans,” 

http://www.lbl.gov/Science-Articles/Archive/L SD-irregular-exercise.html

I want the freedom to know that if I get swamped in work and I can't, I won't gain weight. It's beyond, "You're just not burning as many calories, so eat less."

Trust me when I say that your first year of college will never be SO busy that you don't have 30-60 spare minutes for exercise. Plus the activity is a really good stress release.

If you suddenly stop you probably will gain weight, especially if you keep eating the same number of calories as you were previously as the drop in calories burnt may well mean that you suddenly are eating over your daily requirement.

If you peg back your eating and ensure that you aren't exceeding what you will burn per day in your new lifestyle you should be fine (keeping your diet balanced as well obviously).