Jeremiah Peterson decided to get serious about weight loss when a family hiking excursion last summer proved to be too taxing for his then 290-lb. frame.

“I remember being bent over heaving just trying to catch my breath,” the Missoula, Montana-resident tells PEOPLE. “When I looked up, I saw my wife and three kids [10, 8 and 7] easily hiking, talking and laughing with each other — without me. It was a hard-hitting moment.”

He continued: “I felt sadness and shame in that moment thinking how I had let myself get to this, but so much deeper than that. If I continued to live like this, I would not live.”

When he returned home, Peterson, 39, began researching weight loss options and found a video advertising a transformation challenge. “[It] sealed the deal for me. I signed up knowing I was going to give this challenge every single thing I had,” he says.

Prior to losing weight, “a typical day for me was to not eat all day and then get home from work, drink a few beers and eat a big dinner,” says the antique store owner. “Putting my body into starvation mode and then overeating made my body blow up like a balloon, quite literally. I had constant bloating, heartburn and awful stomach issues.”

After finding out he was gluten intolerant, Peterson switched over to a keto-based diet consisting of healthy fats, lean protein and green vegetables. The new nutrition plan and twice-daily hour-long hikes “made the weight start to pour off.”

He also started weight lifting six days a week, focusing on a different body part each day.

Peterson ended up dropping 82 lbs. during the 150-day transformation contest, called the 1st Phorm Transphormation Challenge — and he won the $50,000 grand prize.

Now 198 lbs., Peterson continues to document his journey on Instagram and inspire others.

“I have so much more energy and I feel like I am always in a great mood. I feel like I have become the dad and husband that I really wanted to be,” says Peterson.  “I feel like I have drive and ambition like I have never had before in my life — and I’m almost 40!”