How can I prevent my teenager from watching too much TV?

In theory yes, in practice it can be a little more difficult.  Adolescence is a period of transitions and transformations with the aim to estabilish their own identity that is separate from their family - this is an evolutionary process and has always been the hallmark of adolescences in humans and across all animal species - what has changed is the social contexts.  This explains in part why teenagers often have struggles with their parents and often do the exact opposite to what their parents ask or expect, so for this reason it can be tricky getting your teenager to change her TV habits.

Ideally, prevention starts at a very young age, before the teenage years, when it is much easier to set good patterns - avoiding TV as a babysitter, being active together as a family, not making the TV and other screens the focus of living areas, making sure screens are not in bedrooms, getting the kids involved with what you are doing (making dinner, setting the table etc, rather than watching TV while you get dinner), setting rules early about when and how long it is appropriate to turn on the TV (only after dinner, only after homework is done, turned off at a certain time, no TV in the morning etc), doing non screen things as a family (board games, cards, gardening, going for walks etc).  All these things and leading by yourself can make it much easier to avoid spending too much time in front of screens as a teenager.

If you have a teenager who is already in this behaviour and you want to change her behaviour, you have to be very smart about it. 

Number one rule, show her respect and talk to her in the way you would like to be spoken to - don't talk down to her. 

Number two, lead by example and invite her to join you - if you are going for a walk, as her, would you like to come with me, if you are getting dinner, ask her, would she like to help you - if she says no, just leave it, ask her again the next day, just like you might ask one of your friends, one day she might suprise you and say yes.  Give her some responsibilty - find something you know she is good at and likes and ask her opinion about it, just like you would a friend and then follow that up by ask her if she would to do that (eg if she likes cooking, say, I would like to cook something different for dinner, what do you think I shoud do and then maybe give her some recipe books and ask to have a look through and see if she come up with something different, then ask her would you like to help me, or would you like to do dinner on Wednesday night, or maybe you ask her opinion about a good walking track or gym class, get her to do some research for you and then ask her if she would like to join you). 

Number 3, spend time with her or enjoy her to spend time with another adult who will set a good example for her - maybe an Aunty, older cousin etc.  Just being with your daughter will encouarge general conversation with it being a formal chat and you maybe be able to have casual conversations about different activities other than watching TV.  Initially, sitting down watching a program with her may help to start some ‘being together time’ and that may flow into other activities - but you need to be careful it doesn't become your habit too!  If the other VIP adult calls her and asks if she wants to come over, or go for a walk or come to gym with them etc, she maybe more likely to go than if you asked the exact same thing - don't be hurt by that, be happy that she is not sitting in front of the TV and that she is with a responsible adult whom you trust.

Number 4, set up a physical environment at home that doesn't centre around the TV, if the TV is one one the first things she sees at she works in the house, it is hard not to stop and watch it, if the couches are set up facing the TV and not each other, it makes it difficult not to stare at the screen, if she has a TV in her room, if it very difficult not to watch it.  Humans generally don't have good willpower, so try to minimise the tempation as much as you can - even ask her to help you re-design the layout of the furniture etc.

Teenagers can be very tricky to deal with, but if you understand what adolescence is all about, you will understand what a beautiful and exciting phase of life it is and I think you will find it a little easeir to connect to your teenager or at least not take some of their behaviours personally - I recommend you read ‘the beautiful brain’ in National Geographic (just google it)  and/or watch the ABC product called ‘whatever - the science of teens’ (available at ABC shops).

In terms of actual activities she might enjoy they are loads - walking, different sports, dance (so many different forms and so many different levels), gym classes, pilates, yoga, shopping (loads of walking when you shop), martial arts, wii fit.

I hope that helps