"The business was doing okay, but I decided I needed to get my life in order and wanted to get healthy again," added Gwilym, who is also a Vo5 ambassador for the NME Awards.
After forming a folk band with his friend several years ago, Gwilym's barber urged him to grow some facial hair to look the part.
In keeping with his new look, the musician decided to clean up his diet and cut out takeaways - but the biggest difference came when he quit his desk job.
Gwilym, who lost weight over the space of five years, explained: "It was the best thing for my health as I stopped sitting for nine to 10 hours a day."
As the weight started to drop off and the now-famous beard started to grow, "shy" Gwilym set up an Instagram account (gwilymcpugh) which boosted his following and helped him get spotted by Welsh tailor Nathan Palmer.
Gwilym, who is now signed with top London agency AMCK Models, was then photographed for a coffee table book, 100 Beards, and was part of the Red Hot Photography project - two gigs that helped his career go stratospheric.
Since then he has worked on campaigns for Vans, Bud Light, Diesel and he's also worked closely with David Beckham thanks to his Haig Club whiskey project, as well as being an ambassador for Beckham's new male grooming brand, House 99.
Reflecting on his newfound fame, Gwilym said: "Having worked in finance for years, the opportunity to work with creative people and travel around the world is amazing. But you forget how nuts it is, it all becomes normal.
"I think I'm lucky I got into this profession at the age that I did. I try not to get caught up in it all and my girlfriend helps a great deal wit that."
A keen photographer, Gwilym is hoping to make his own mark on the world with his pictures, taken while travelling the globe.