Just over a year ago Steven Begley of Cardiff was eating only fast food, was reluctant to get off the couch, ordered his clothes online and weighed 158 kilograms.
On May 2 he set himself a challenge: to weigh less than 100 kilograms by New Year's Eve.
He lost 10 kilograms in the first week, exercising up to 75 minutes per day, and was down to 97 kilograms by Christmas.
Mr Begley said he went to the gym at 1am to avoid the stares of onlookers.
"It was the only time of the night I felt most comfortable being in a gym - when nobody else was there to see me," he said.
"I started on the treadmill and after a while I did some weights as well, and some cross training, and I bought some scuba diving gear and gave myself a challenge to become a dive master."
Mr Begley passed that test yesterday.
After losing 72 kilograms he now weighs 86 kilograms and is maintaining his weight.
Today he takes on another challenge, this time to raise money for Camp Quality.
From 8pm he aims to walk 72 kilometres with 72 kilograms strapped to his body, shedding one kilogram per kilometre.
He hopes to raise $20,000 and estimates it will take him about 18 hours to complete the challenge. He will be streaming live on atustream.tv/channel-popup/challenge72 with support from his girlfriend and a team from Anytime Fitness at Warners Bay.