A support worker who gained 9st when he gave up sport has lost 6st in six months after switching fast food for Full English breakfasts.
Liam Smith saw his weight increase to 19st when he stopped playing badminton and football.
He decided to make a change after he had to buy an XXL shirt to wear for his 25th birthday celebrations.
Liam has lost an average of one stone every month since trading in his daily fix of microwave burgers and takeaway curries for grilled bacon and fat-free yoghurt.
He has now been named Slimming World's Mr Sleek 2017.
Liam, from Normanton in West Yorkshire, said: "When I was at school my whole life revolved around sport.
"I played badminton for East Yorkshire at county level, was in a football team every weekend and was studying Physical Education at A-Level.
"I chose to study theatre at university and left sport behind though, and that's when I began to gain weight."
Within a few years Liam went from being an athletic 10st teenager to an unhealthy 19st.
His confidence fell, he found it difficult to find clothes to fit and hated seeing photos of himself so much that he often 'untagged' himself on social media sites.
It was in May 2016 after celebrating his birthday weekend with his friends - and having to buy an XXL shirt for the special occasion - that Liam decided to tackle his weight problem.
He said: "I'm originally from Bridlington and my friends had come to visit.
"We had a really unhealthy weekend - McDonald's breakfasts, takeaways, lots of alcohol - and the moment they went home I knew I had to do something about my size."
Overweight men see drinking lots of alcohol at once and eating typically high-calorie foods like meat pie and fried breakfasts as 'masculine', according to Slimming World.
Liam said: "Luckily my mum was joining Slimming World the following week so I made her promise to take me along."
Donna, who has also lost 2st, took Liam to a nearby slimming group as promised.
Liam said: "I was so nervous that first night because it didn't feel like something many males in their mid-20s do, but everyone was so welcoming and before long I considered them friends.
"I was excited too though because I knew people said Slimming World worked so I was eager to crack on.
"I'd only ever tried losing weight by eating healthily and exercising on my own before and I'd never managed to keep it up longer than a few weeks.
"This time I really enjoyed the support I got and feeling like I was inspiring other people, too.
"Our group's like one big family."
Following Slimming World's Food Optimising plan Liam has learned how to cook homemade versions of his favourite burgers and curries.
He said: "Eating for me used to be about comfort food and laziness.
"I enjoy cooking now and regularly cook for my best friend who I live with too - he's lost 2st just by eating the same meals as me."
While overweight men see physical activity as the most socially acceptable way to lose weight, many say they struggle to do this in reality.
But Liam has joined a local football team, started playing badminton again, joined a gym and also enjoys walking and cycling.
His ambition now is to train to become a football coach so he can one day help his two-year-old brother Charlie in a team.
Liam also wants to try skydiving and bungee jumping - activities he'd previously been too heavy to attempt.
Six months after starting at Slimming World Liam reached his target weight of 13st.
His mum, stepdad Paul and sister Bethany have also lost a combined weight of 5st between them.
Men lose more weight than women at Slimming World on average - 5.7 per cent body weight in 12 weeks compared to 4.3 per cent.
Liam says he hopes his title as Slimming World's Mr Sleek 2017 will inspire more young men to tackle their weight.
He said: "I'm much more confident and I love sharing pictures on social media now.
"Since seeing what I've been able to achieve lots of people I know have started slimming too.
"I feel so passionate about it that I've decided to open my own Slimming World group to help more people lose weight like I have."
Breakfast: McDonald's breakfast
Lunch: Pre-packed sandwich
Dinner: Takeaway curry or ready meal
Snacks and treats: Microwave burgers, chocolate, crisps, sausage rolls, beer.
Breakfast: Big plate of grilled lean bacon (visible fat removed), mushrooms and tomatoes, scrambled eggs and baked beans, with wholemeal toast
Lunch: Chicken salad or homemade omelette
Dinner: Homemade lamb kofta curry with potato wedges (baked in the oven in low calorie cooking spray) and vegetables
Snacks: Fresh fruit and fat-free yogurts
Treats: Sauces with meals like tomato ketchup and mayonnaise and a beer