I agree with paynes mom, definately call the doctor just to at the very least ease your mind that there is nothing else going on.
Meantime, I would make a game out of this. I wouldn't remove all snacks from the house though but maybe lock them up somewhere he can't get to them, the idea is that deprivation of yummy unhealthy snacks doesn't really work, but a little indulgence once in awhile doesn't hurt and is actually good because you are teaching moderation in indulgent things.
I would create a richard simmons style diet where you give your son a list of the foods he can have each day, break it down to 3 meals and 3 snacks, then break it down to what he can have in each category,
Here's a similar topic on our forum, which you might find helpful:
http://www.autism-pdd.net/forum/forum_posts.asp?TID=14714&am p;KW=insatiable
One thing I might suggest for excercise that he may not realize is exercise is to geta video game station like PS2 and let him play dance dance revolution or other games that require movement. The WII system is also great for this. In the rainy season here it is very hard to take my boys out to exercise so I let them do this for a half hour a day and they burn quite a few calories. The other thing you have to remember with teenagers and the human body is that the teenage years are the years kids do alot of growing in height. I would talk to your doctor if you are truly concerned and then try to find something fun that he will do to get the exercise in. Good luck. My son is a teenager, and is always hungry. I wouldn't care, but he's also overweight and inactive. At his age, it's pretty hard to force him to do exercise, although we try. He also has a very narrow range of food he will eat, and all of it is bad for him. We have cleaned the house of junk food and have limited his portions. Yesterday he said, "I'm depressed because of this diet." I felt terrible because he doesn't have that drive to look good/be healthy that "typical" kids have, and I'm afraid he thinks we're punishing him. He really is way over the weight he should be and I'm afraid he'll be a three hundred pound adult if we don't help him control his appetite. He is not on any medication so it isn't that. He just wants to eat all the time. You might want to talk to his regular doctor about this...it could be something triggering the eating...medically. Is it emotional eating?
Mia, will your son wear a pedometer? Maybe you could set a goal together with him of say 2000 steps per day and then increase it over time? or maybe a day where he gets to choose all his meals, but the other 6 days he has to try and eat what you prepare?
Nicholas has a very narrow diet so a few years ago I made a chart that had a list of food (like a pyramid) and we listed how many times a day/week he should be eating from each category. Then we made a deal:- if he did say 20 minutes of walking he could have junk food of his choice, or a bowl of ice cream etc. It worked really well at the time.
With Lachlan I have had to remove all junk food from the house (not easy because I work for a snackfood company!). If he sees it in the house he cant focus on anything other than eating it.
Good luck!
Mysh
Does your son snore? If so, he could have sleep apnea. One symptom of that is being overweight, because the hormones that control appetite are affected by sleep. And the apnea gets worse with weight gain, making it a vicious circle. My husband was diagnosed with this as an adult, but about 2% of children have it.
Here's an article about snoring and sleep apnea in children:
http://pediatrics.about.com/cs/conditions/a/snoring.htm
Again, good luck with everything.