Brock Carrow, from Florida, weighed 37.5 stone (238kg) before one day he had a 'lightbulb moment', and decided to take charge of his health.
The 36-year-old university worker said he'd always had trouble with his weight, but when his mother died in 2006 he partly blamed himself, which led him to turn to food for comfort.
He said: "I always held it in my head that I could have done something to help her not succumb to alcohol addiction. At the time, I was playing music in a relatively successful band in the USA, so I just ignored those feelings and ate them to deal with them."
He said he lived on a diet of pizzas, kebabs and sweets, totaling around 5,560 calories a day.
But all that changed when he read about a former Navy Seal.
Brock said: "I was reading an article in some paper with a former navy seal, David Goggins, and the drive in his story made me do a little research on him and there was something he said that clicked with me.
"He said, 'when I die and I go before whatever deity that will judge me and they look at my name and in the book it said all these amazing accomplishments I would stop this deity and tell them that they must have my story mixed up with someone else's life.
"The deity would look at me and say, 'oh no... that's who you were supposed to be if you worked harder'."
Deciding to turn his life around, he researched new diets and tried to find a personal trainer.
He said: "I tried every diet there was. I was turned away by more trainers than I knew what to do with because at 525lbs (37.5 stone), not too many personal trainers have experience in dealing with someone of that size."
Eventually, Brock said he decided the only option left was to have a Vertical Sleeve Gastrectomy fitted, which he did in April 2017.
After three months, and a loss of 60lbs (27kg), Brock started exercising, doing light cardio and small amounts of weight training, losing 100lbs (45kg) over the summer.
Brock now weighs 18.9 stone (120kg) and works out regularly, jogging five to six days a week and training with his PT twice a week. He's also adopted a calorie-controlled diet.
Brock explained: "For breakfast, I eat Anabolic French toast, for lunch it's lavish bread flatbread pizzas or a big salad. Snacks are Orville Redenbacher Smart Popcorn and, if I need something sweet, I will make anabolic ice cream, which has no dairy but is a lot of protein."
Since losing the weight Brock says his confidence has never been higher and he now hopes to work for his local police department pending a physical test.
He said: "I'm setting new goals every day that in a thousand years I never thought it would be possible that I could achieve. I push my mind, my body, and my spirit harder than I did the day before."