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Disordered eating isn't always easy to detect yet it affects about 30 percent of teen girls, 15 percent of teen boys and many in the transgender population.
So what are the warning signs that a young person has an unhealthy relationship with food?
Parents should look out for not only what a teenager is or is not eating, but also any rigid rules around food or irritability at meal times, clinical psychologist Catherine Gallagher said.
"Have they become picky or they're restricting their food types? Are they cutting up food into tiny pieces? Are they weighing food? Are they often saying they've already eaten? Are they skipping meals? Are they disappearing after meals and spending time in the bathroom? Are they doing extra exercise?"
Parenting: how to talk about body image issues with teenagers
If you're concerned about your teen's eating, the first port of call is a GP where they'll first be weighed and checked for anything else physical that may be going on, Gallagher said.
"Just get a baseline, get in there and get the GP has been part of the team.
"Your young person might fight you on this because their brain and body is saying 'Look, I look absolutely fine and in fact, putting on weight has become dangerous to me and staying slim has become my safe place.'"
Disordered eating often kicks off when weight loss is met with positive comments, Gallagher said, especially if a teen is a bit vulnerable, anxious or perfectionistic.
"[They may think] the whole rest of my life feels chaotic and out of control but this is something I can succeed at - controlling my eating or controlling what my body looks like'. There's a reduction in negative feelings as a result of that."
If your teenager is a bit overweight, look at whether they seem happy and social and emphasise the benefits of a healthy lifestyle.
"[For example] It's so important to get sunshine, to be social, to rest, relax, get some exercise, and have food that fuels your body.
"Have that 'dilemma' approach of 'Look, I don't want to offend. I'm probably going to say this wrong, you're probably going to get really annoyed with me, but I'm just a bit worried.'"
Be curious with them about their relationship with food and use the data.
"Dip in there and go 'Hey, do you struggle with this stuff? … I heard you say this, or I noticed you're doing this. It's really, I'm really sorry you're feeling that way. It's really tough that you feel that way.'
"This isn't a big stick to hit parents over the head with but if you're worried about a young people's behaviour, it's really important to look at your own beliefs.
"Are you commenting on people's weight or how good people look when they've lost a bit of weight? Are you obsessing about it? Am I doing lots of baking and cooking but not actually eating it or having difficulties deciding what to eat or portion sizes?"
"If you do say the wrong thing and commend someone's weight loss, catch yourself and use it as an opportunity.
"You could just go 'Whoa, do you notice I just caught myself there?' We all fall into that trap.
"Come back to them afterwards and go 'Hey, I noticed I said that. I've grown up in the environment that you have, too so I can be influenced by these things as well."
Gallagher sees now that in the past her own fears have influenced her communication as a parent.
"If we don't keep track of our own anxiety then how do we not get preachy? We have to rein in our own anxiety to be able to have these conversations in a more settled way.
"We're not going to get it right, we're going to bumble over it but those conversations become a lot easier when we've got a relatively okay relationship.
"If the only conversations we're having are the serious ones, then they're not going to talk to us, and we probably feel highly anxious talking to them."