In her teen years and early 20s, Fiona Falkiner was convinced her weight stood in the way of her living a happy life.

“There were so many things that I was just too scared or too embarrassed or didn’t think I was fit enough to do,” Falkiner recalls.

“I used to go on holidays with friends and not do a thing. In Thailand, all my friends went trekking and I thought, ‘Well, I can’t do that’ so I just stayed on a beach with my sister instead.”

These days, this scenario is hard to imagine. Since she placed fourth in The Biggest Loser‘s first season in 2006, Falkiner has gone on to host the show and become an international model and brand ambassador for Trimfit Bodies and Target.

When she’s not doing all that, she’s using her social media platforms to spread messages of body love and health to her thousands of fans.

Yet Falkiner was once plagued by insecurities about her own appearance. “I blamed all of my problems, all of my insecurities, all of the stuff that was going on in my life on my weight. I always had it in my head [that] ‘if I lost weight, my life would be perfect’,” she tells Mamamia.

Watch: Meghan Ramsay on the effects of negative body image. (Post continues after video.)

Superficially, Falkiner found the solution to her troubles by signing up for The Biggest Loser. The then-23-year-old shed a staggering 30 kilograms on the program, taking her from a size 20 to a size 12.

This was quite a feat, yet Falkiner couldn’t understand why her new weight hadn’t automatically translated to a new mindset.

“I stepped out as a skinny person but all of those problems, all of those feelings still existed… I was probably more miserable than previously because I realised that I hadn’t fixed the problem. It was still there,” she explains.

“It was quite a confusing time because I was supposed to be extremely happy and feeling amazing, but I wasn’t.”

This “low period” was exacerbated by the pressure Falkiner felt to maintain her smaller dress size — it got to the point where she didn’t want to go out in public except to get to work.

Eventually, she booked herself in to a health retreat, where she found herself in tears during a counselling session. “I realised that I needed to make some changes and actively change my mindset. I needed to learn to love my body,” she recalls.

One simple practice that has helped her reach this acceptance was positive affirmations. Each day, Falkiner committed to reminding herself about the goals she’d achieved, that she was a powerful woman, that she could achieve anything.

Falkiner has also retrained herself to resist the all-too-common urge to pick apart her appearance, by giving herself a compliment each time she looks in the mirror. (Post continues after gallery.)

“When you go out looking all lovely, and a guy might give you a compliment — how nice does that make you feel? So I figure, ‘why don’t I do that to myself? Why do I need to wait for somebody else to make me feel good?'” she says.

In her role as Trimfit Bodies’ Healthy Mindset Ambassador, Falkiner is committed to sharing the message that positive thinking is key to wanting to live a healthy life.

This is something she knows from her own experience — anyone who follows her on Instagram knows she’s passionate about keeping active and looking after herself — but also something she’s observed among the Biggest Loser contestants she works with.

“You do want to train. You do want to eat well. You want to nourish your body. You’re not in that negative headspace thinking, ‘Food is the enemy, I want to punish my body’,” she says.

After work workout…the struggle is real! But I know how well I will sleep tonight! @trimfitbodies #healthyisastateofmind ???????????????? #stilljetlagged

A photo posted by Fiona Falkiner (@fionafalkiner) on May 9, 2016 at 3:56pm PDT

This isn’t always an easy attitude to cultivate. None of us exist in a vacuum, and we’re constantly exposed to messages about our bodies and how they should look.

Whether consciously or not, health is so often associated with a specific body image; one that’s lithe and toned and taut enough to bounce a coin off. That might be the reality for some people, but it’s not an across-the-board experience.

Falkiner admits it’s hard not to compare her own body to others’, especially when she’s at the gym, but she realised there’s no point chasing an ‘ideal’ that’s not achievable.

“I train with a group of people who are very fit. I’m a size 16 — when I jump around, things move. The likelihood of me achieving the body type that they have is pretty much slim to none,” she says.

Image: Getty

"I'm not the fittest, I'm not the strongest, but I go in there every day to train and I'm just training against myself. I'm trying to beat my personal best."

Reflecting on those early years of feeling uphappy and insecure, Falkiner wishes she could go back, give her younger self "a big hug", and tell her not to be so hard on herself.

"This body is the only body we have, so you should be kind to it and look after it and respect it. Part of that is looking after your mental state," she says.

"If you're in a really low place and can just slowly change your mindset around it, and really start embracing life and going for it, all the other things come into play."

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Featured image: Getty.