Going from being overweight to rippling abs is something that can seem like a distant dream for a lot of people, but for one California man it has become a reality.
Zack Vogler, 24, grew up obese and was facing down a life of unhealthy living when he was diagnosed as having both diabetes and hypertension as a teenager.
"I've been obese my whole life leading up to when I lost weight. I come from an obese family with a history of all the weight-related issues you can think of," he said.
"I definitely learned habits from my male role models we always put a lot of value in being big, strong and eating a lot. I also turned to food for comfort, when my parents got divorced and when my older brother was diagnosed with leukaemia two years later."
"I was always self-conscience about my body, I didn't feel like I was attractive at all. I felt trapped in a huge body that I hated," added Zack.
When personal tragedy struck, he felt like he had to do something to save himself from a similar fate.
"After my father had a heart attack in 2012, I started looking into my own health," explained Zack.
"Being 463 pounds at 19, I was worried that I was headed down the same path as my father. I went to the doctor and was diagnosed with pre-diabetes, hypertension and put on blood pressure medications. That's when I knew I needed to make a change if I didn't want to die from obesity-related illnesses."
Zack changed his eating, began exercising and managed to get himself down to half of his previous weight - from 33 stone to around 15. He lost so much weight that he had to undergo almost £15,000's worth of plastic surgery to rid himself of the skin that he had accumulated.
It was all worth it, he says. Zack explained: "I no longer feel trapped in my body, I'm so much more comfortable in my own skin. I like to wear tighter clothes and I'm proud of the body that I worked hard for."
Zack now works as a personal trainer and helps others along the journey that he took.
He says: "I also have so much more energy and I've found my passion in life and made a career out of helping others achieve what I have. I lost the weight by tracking my calorie intake and exercising.
"I completely changed what I ate. I quit drinking calories and started eating more lean meats, vegetables and just whole foods in general. In terms of exercise, I fell in love with lifting weights. I lifted a little in high school for football, but I never got that into it, now it's one of my favourite things in life.
"I had to remind myself everyday of where I came from and what I wanted to achieve. I definitely fell off the wagon a few times, but I never gave up on myself or my goals. People honestly don't believe it. The people I used to know don't even recognise me anymore and those I met after weight loss can't conceive how I was ever that big."
There is no great secret, he says, just perseverance. Zack says: "Start small and start with your diet. What you eat is why you're overweight. Don't drink your calories; track your food, monitor your calorie intake and start taking daily walks."
"I love myself and I am now proud to be me."