“It would get to me a lot of the time. I mean, I would come home and cry sometimes. Especially because I had no confidence back then. I thought what they were saying was true. I was a whale, or extremely obese, or a waste of air,” she recalled.
She tried dieting and searched for ways to lose weight. At some points she tried starving herself and when that failed she would binge-eat when her family wasn't looking.
“I thought maybe if I don’t eat for a couple days maybe I’ll drop three pounds and I’ll look better than I did the day before,” she said.
Eventually she hit rock-bottom and resorted to self-harm.
“When I found she was cutting, because I saw it on her arms, I just… I literally couldn’t breathe,” Kiersten's mother Sherri Zimmermann said.
“Maybe this’ll make me feel better,” Kiersten told herself at the time. “Or maybe this will let the pain go away and maybe this will stop. If they see the marks on my arms, they’ll just stop bullying me.”
Her parents intervened and with the help of a counselor put an end to the cutting.
While babysitting a 5-year-old child, she was eating pizza pockets and the kid told her she was fat. This was when Kiersten started her weight-loss journey and shed nearly 100 pounds in a transformation that changed her life.
“People always say kids are honest,” she said. “That was the day that I started changing my life.”
At her heaviest she weighed 230 pounds and struggled with simple movements, including walking.
"Before my journey I felt insecure, I had low confidence, I wasn't motivated and walking was extremely hard for me without becoming out of breathe and needing to sit down, it was a nightmare," she told Daily Mail Online.
Starting in 2012, at only 13-years-old, she made drastic changes to her lifestyle including her diet and exercise regimes.
After trips to the gym, she quickly started to lose weight and later discovered that she had a passion for weightlifting.
The now 18-year old wants to help inspire others as a personal trainer.
“I tried eating right, working out, weight-loss pills, tried not eating. It seemed like nothing worked. Even cutting to help – don’t do it OK?” she wrote in a video.
The video of her transformation has been viewed thousands of times and inspired many young people.
“I’ve had so many people say ‘you motivated me to start eating healthy,’” she explained. “It’s amazing to feel that I do have that power, especially on young girls and teenagers.”
She has set a goal to compete in an all-natural body-building competition in October.
“I wouldn’t change any of the bullying that happened to me, the pain I felt and the tears I cried. All of that made me who I am today – a strong, confident, motivated young woman who is determined to help others accomplish their goals in life.”