Shop girl, I did a search on weight loss & fitness forums for teens, and the ones that appeared to not be pro -ana/bullemia are the sites I am posting. Some of these had more of a general teen health feel to them with some postings on wl/fitness, nutrition, etc. Hopefully something here will help you or lead you where you are comfortable.
Also all of these are free forums I found. I know as a teen I did The Firm & was part of their forum, which has now been changed to a $10 per month forum. They didn’t have teen specific then, but since there are a lot of teens doing Firms, this may have changed, but I am not sure. That site is
http://www.firmdirect.com/GT/index.j...&prdId=rl00001
http://www.toneteen.com/
Here is one that appears to be primarily for teens with PCOS, so it may not be what you are looking for though.
http://www.soulcysters.net/forumdisplay.php?f=28
http://www.golivewire.com/forums/for...n=teen&forum=8
http://www.spankmag.com/f/disp_section.cfm/cc.73/p.htm
I didn’t see anything specifically for weight/fitness, but you might try searching over in case I missed it.
http://www.teenspot.com/
http://teenforums.studentcenter.org/viewforum.php?f=19
http://boards.self.com/forum.jspa?forumID=2&start=0
http://forum.lowcarber.org/archive/index.php/f-120.html
Here is one for vegan/thinking of becoming vegan teens.
http://www.vegfamily.com/forums/foru....php?forumid=6
These two links – the first one seems to be adult and teens with fitness/wl/health questions, the second is for Teen Health & Life, but again, I did not see much on wl/fitness, the first link had more teen posts from what I looked at.
http://www.afraidtoask.com/ubbthread...&Board=fitness and
http://www.afraidtoask.com/ubbthread...ard=TeenHealth
Here is a BFL one, but it looks like not much activity goes on there.
http://teen-terminal.com/forums/cmps_index.php
This forum has a wide range of teen topics, not just limited to wl/fitness, but here is the link to the 3 teen health forums.
http://www.teen-support.net/forums/i...?showforum=292
Here is a site that has a variety of topics, I did a search for weight loss, and this is what I cam up with, so you might want to look over it in more detail in case I missed anything.
http://www.beliefnet.org/boards/search_results.asp
Again, wide topic range for teens.
http://forums.govteen.com/
I am a member of this forum, prior to it changing to this new format, I think there was a teen forum, but I do not see it listed now. If you contact the admins, they may reopen it, but here is something from there archive.
http://theweighwewere.com/category/teens/
Teen specific, general health- fitness/wl issues are posted here.
http://www.rouseindahouse.com/forumdisplay.php?f=26
Same Deal with this site.
http://www.teencreek.org/cgi-bin/com...l?board=health
Not sure about this one, you have to register & be a member to view & reply to posts.
http://s4.invisionfree.com/kickassboards/index.php
http://www.fitteen.com/
ARE there any teenagers here?
I don't see that name too often. 
It wasn't THAT long ago that I was a teenager myself. 
