Mark tipped the scales at 29 stone, but after shedding the pounds, he now weighs in at 19 stone.
“I’ve still got a way to go. It turned out a couple of years ago I wasn’t far away from being nondiabetic,” he said. “I got pretty close to it. Unfortunately, I let myself go a bit because I didn’t know at the time.”
The Chase star has since teamed up with Fitbit and Diabetes UK – the leading charity for people affected by diabetes – for the One Million Step Challenge to encourage participants to take 10,000 steps a day.
Beat The Chasers airs tonight on ITV at 8.30pm.