When I began my career as a television journalist, I had no idea just how helpless you can feel when being attacked by someone who gives you no room for reply, writes Whitney Fitzsimmons.

Bullying is very serious. Sometimes it's so serious that by its very nature it brings about such a heavy level of shame on the target that nothing is ever done. The victim suffers in silence because of that shame. It creates a paralysis. Nothing is ever said. Nobody ever knows. The perpetrator walks away and the target is left wearing a deep and invisible wound. It is lonely and isolating. That is what happened to me.

It was in the ABC newsroom, it was summertime and it was the beginning of a new year. In my pigeon-hole there was a simple white hand-written envelope addressed to me. It looked benign and non-threatening enough, so I stood there and opened it. Had I known what it contained I would have made sure I read it in private. There scrawled in black ink on the white page was a message informing me that I was too fat to be on TV, that I needed to lose 30 kilos immediately, and that I didn't have the right to be presenting the news.

As I stood there and let this sink in, I could feel my skin burn with embarrassment; my eyes starting to sting as tears began to form. It felt like I was naked and covered in caustic soda. I desperately tried to compose myself in that room which was full of my colleagues. I timidly looked around to see if anyone noticed my reaction or the neon sign that was now hanging over me which screamed "YOU ARE FAT, YOU HAVE NO RIGHT!"

Over the following weeks I received several more letters of "tough love" from this couple in Perth which never of course included a return address. Each time I knew what I was in for but I was compelled to read them.

You see, the interesting thing about bullies is that they know instinctively how to strike at the heart of their target's insecurities. Believe me, these letters weren't telling me anything I didn't know. If we look at the Nigella Lawson-Kate Moss sliding-scale of body shape, I have always been on the domestic goddess side. That is a fact, and when it comes to this, I am my own worst critic.

Those letters have since died down, but there is another force out there, and that is social media - namely, Twitter. I like many of my colleagues and peers have been in the direct firing line of the twittersphere.

Just recently I co-hosted Weekend Breakfast on ABC News 24, and I can't tell you the wave of relief that came over me when, after three and half hours of live television, the social media producer told me that Twitter had been positive. Twitter is the social media sniper rifle, and when you are in television, you can often feel like you are in its crosshairs.

Being the subject of someone's critical eye when your job is to be the conduit for information is a strange sensation. It is for me an unexpected sensation. Call me naïve, but when I started presenting live television 10 years ago, I didn't expect it to be about my hair or my make-up or my weight. I actually thought (and I still do) it was about being pleasant and professional with a touch of warmth and telling good stories. What I didn't expect was to feel so exposed. I didn't realise how helpless you can feel when you are being attacked by someone who gives you no room for reply.

A wise person once said to me that if you raise your head above the parapet, someone is bound to take a shot at it. I guess that's the deal you make when you choose a career in the media, whether you know it or not and whether you like it or not. It's certainly not something I had considered or even thought about when I embarked on this line of work.

Don't get me wrong, I can handle well-thought-out warranted critiques of my work. But my size has no bearing on whether I am good at my job. Staying at a certain weight is not in my KPIs, and being this size has never been an impediment to my career. But what I do know is that my weight is directly linked to how afraid or vulnerable I feel. As strange as it sounds, for me, carrying extra weight feels like protection or amour and it allows me to hide in plain sight.

It's taken me a long time to get to the point where I could feel comfortable talking openly about this. I am not complaining about my career; in fact, it's great and I love it. But while I have learned to deal with this, what I want to make clear is that we all have problems, vulnerabilities and suffer from the vagaries of life. None of us is immune from episodes of depression, which is something I have also experienced and thankfully was able to work through with a therapist.

Some people aren't so lucky and this type of severe scrutiny can lead to tragic circumstances as we have seen in recent days.

Whoever wrote that nursery rhyme "Sticks and stones may break my bones, but names will never hurt me" got it wrong. Words can hurt, they can hurt very badly and they can take a very long time to heal.

If you or someone you know needs help, call Lifeline on 13 11 14.

Whitney Fitzsimmons is an ABC newsreader and the presenter of Business Today on ABC News 24. View her full profile here.