"I was born and raised in Missoula, Montana — you know, the River Runs Through It place," Peterson told MensHealth.com. "Growing up in the ‘80s, I was one of those kids always outside building forts, fishing, playing war, playing sports with all the neighbour kids."
Peterson was also being bullied at school, so he wanted to get fit to protect himself and "anyone else that couldn’t protect themselves."
"In junior high, I made the decision to not get knocked around anymore," he said. "I practically lived at the local Y lifting and shooting hoops. I chose then, at the age of 15, to get stronger and gain confidence within myself."
Because of this love of sports, Peterson went on to also gain a degree in coaching from Trinity Bible College in North Dakota. After graduating, he opened a small personal training studio in Scottsdale, Arizona. There, he met his wife, who was a yoga instructor.
The two married and had their first child together, a son, before deciding to move back to Montana. Instead of continuing his personal training business, the couple decided to open an antiques store, which "became our only focus," Peterson said.
He soon fell into the day-to-day trappings of owning a family business, letting his love for fitness fade into the background. He stopped going to the gym — and every night after the shop closed, he'd sit around drink a few beers.
"My desire to hike and fish, the very habits that I had created so many years ago, slowly disappeared into the process of building a life and a business," he said.
Peterson found himself withdrawing from everything, including taking family photos and spending time in the mountains with his children. In 2017, at 40 years old, Peterson weighed 130 kilos — and one fateful day, he realised he couldn’t hike anymore with his 10-year-old and 8-year-old.
"On a particular backpack hiking trip out in the mountains with my family, I had a kind of 'aha' moment," he said. He was out of breath, feeling chest pains as his kids continued on without him. "I reflected on what my life had been. I thought about what my life was at that very moment, and saw what I wanted my life to be."
The first change Peterson made was to think about the food he was putting into his body. Like many guys looking to transform, Peterson took on the keto diet, which entails eating 60 to 80 percent of your total calories from fat, around 15 percent of your calories from protein, and less than 10 percent of your calories from carbohydrates.
This alone "made such a tremendous change in how I felt almost immediately," Peterson said.
Next Peterson cut out all alcohol (just like Zach Galifianakis, Ed Sheeran, and Jonah Hill, who all credit their weight loss to giving up booze).
Finally, he began to exercise once again — not in the gym, but in the great outdoors.
"I hiked every morning and every evening with my dog in the mountains that I loved so much as a kid growing up," he explained, adding that his hikes usually lasted about 40 minutes apiece. He slowly implemented a weight routine, lifting weights five or six days a week for about an hour a day on his lunch break. (If you’re looking to get started in the weight room check out our 3-week beginner’s guide here.)
Peterson ended up losing 40 kilos in just five months, dropping from his heaviest of 130 kilos to 89.
"I lost the weight just doing what I love," he said. "I know it sounds simple and it is, really it is."
Now, he's hoping to inspire other guys — and it appears to be working. His Instagram account, @jeremiahpetersonmontana, has amassed more than 36,000 followers. His inbox is always flooded with people asking for advice, which he’s more than happy to share.
"I receive thousands of amazing messages of hope, gratitude and encouragement every day," he said. "Those messages make this change in my life into something so much bigger than I ever dreamed or expected it to be."
This article originally appeared on Men's Health