"My father is my trainer. He brought me to the gym at seven years old and since then I never stopped," says Mermoux, who hails from Contamine-sur-Arve, a French town on the border with Switzerland.
"In life in general, I like to do things which challenge you to face your fears and overcome them. This is what I like about fighting, I think.
"Since my amateur days I just tried to challenge myself more and more, taking on harder levels of opposition and fighting on bigger platforms so there was more pressure, seeing what I could handle and how I handled it."
Mermoux is serious about his training and regularly travels to other locations to train with new coaches. He spent the first half of 2019 in Vancouver, Canada to train with Josh Jauncey and his team.