I have always been overweight. I was 10lb (4.5kg) when I was born and it kind of went from there. I was 10 stone (64kg) by the age of 10, 13st (83kg) at 13 and 16st (102kg) by 16. My age and weight matching was a worry – and lasted until I was 21.

There were diets along the way. When I was younger, my parents tried various approaches to get me to lose weight – gentle persuasion, desperate pleas, even financial bribes. I was referred to a hospital dietitian who had a go, too. When I was a bit older, I joined a gym, and throughout my teens and at university I tried whatever fad was going: SlimFast, the Atkins, the GI diet and its closely related Low GL version. I went through a phase of drinking grapefruit juice after every meal because I had read it stopped any fat eaten being absorbed, and I once spent a hungry fortnight eating nothing but Rice Krispies after vaguely recalling the Olympic sprinter John Regis explaining how he had managed his weight by eating only cereal. Unsurprisingly, it did not work.

When I was 21, a friend at university told me he was concerned about my weight, that I was making life difficult for myself. I wasn’t offended, but those words were a kicking-off point. I lost almost four stone over the course of that summer.

Yet the way in which I had lost it – walking eight to 10 miles a day in my summer job as a hospital porter and going to the gym most days – couldn’t last and, within two years, the weight had returned. I made countless resolutions to slim down over the next few years, but nothing stuck.

At 30, I tried Weight Watchers for the first time. Again, I lost 4st in a matter of months but, happy in a new relationship, I took my eye off the ball, enjoying eating out and cosy, snack-filled nights in. The weight crept back on. By the middle of 2016, aged 35, I reached my heaviest ever – 21st 4lb (135kg).

Something felt different this time. I was unhappier than ever about my weight and, as I marched towards 40 (sweating and out of breath), I felt I was being stalked by the twin spectres of diabetes and heart disease. A lifestyle overhaul was needed, not just a diet.

In my youth, despite my size, I had always been active. I was in the school and town football and rugby teams and I was a county tennis player. But that was a long time ago. According to a 2017 report by the European Commission, 37% of people in the UK don’t do any exercise, and I was among them. I quietly longed to get back to sport but had convinced myself that my knees couldn’t take it, or that I should lose some weight first, then go running, or that I would let the side down and no one would play football with a big fat man. There’s always an excuse when you are trapped in a cycle of guilt, self-hatred and emotional overeating. Much easier to buy another bag of wine gums, fire up Netflix and promise to start afresh on Monday.

Andy Welch in 2008: ‘I made countless resolutions to slim down over the years, but nothing stuck’

Then I stumbled upon Man v Fat, a weight-loss football league where overweight men can play against each other, safe in the knowledge some skinny wunderkind isn’t going to show up and run rings around them. Players are rewarded for weight lost with goals added to their team’s score on the pitch. There are hat-trick bonuses for losing three weeks in a row, and further rewards for hitting 5% and 10% weight-loss milestones.

I signed up in January 2017, unsure what to expect and having not kicked a ball since my late teens. The registration meeting was heartening for a number of reasons: I was far from the biggest man in the room – a rare feeling – and most of the players returning for their second run had lost 10% of their body weight during the previous season, showing me that change was possible. After the initial introductions, we began swapping stories of our struggles with weight and our reasons for wanting to lose some. It felt more like a therapy group than a Sunday-morning kickabout.

At my first weigh-in, the scales read 20st 7lb (130kg). Six seasons later, I have, as of last week, broken through the 100kg barrier for the first time since I was about 15. My blood pressure has dropped (from 140/90 to 120/80); I am in 34in jeans, whereas I once wore 44in, and I have a resting pulse of about 50. I also bought the Baracuta G9 Harrington jacket I had lusted after since my teens but could never squeeze myself into without looking like a burst sausage.

I now play football three times a week, have taken up running, go to boxing classes and have started playing tennis again, 20 years after I stopped because getting around the court was too difficult. Another new pastime is, when I’m in a supermarket, piling up sacks of potatoes so I can lift my missing 35kg and try to remember what it was like lugging it around. I’m sure the staff hate me, but at least I am enjoying myself.

Gaining control of my diet has significantly improved my mental health, too, boosting my confidence, resilience and previously nonexistent self-esteem. It was tested to the extreme during a devastating 10-week period last year that saw the breakup of a long-term relationship and the deaths of a grandparent and a dear friend. The more life events spiralled beyond my control, the tighter my grip on the double distractions of meal planning and exercise. In traumatic times of old, I reached for drink and ice-cream. Now, I eat fruit and play football.

Andy Welch in 2019, having been playing in Man v Fat for the past two years. Photograph: Graeme Robertson/The Guardian

Exercise is, of course, important to weight loss, but controlling intake is vital. For that, I use Weight Watchers’ app to track my food, double-checking calorie consumption with MyFitnessPal. I rarely drink alcohol and, despite a sweet tooth that could shame Augustus Gloop, waved goodbye to my beloved pick’n’mix. I am not yet at a healthy weight (my goal is 13st 5lb, or 85kg), and whether I will achieve that is another matter. I know I’d like to.

Andrew Shanahan set up the first Man v Fat league in Solihull in 2016. Two years previously, after losing 6st, he had written a book, Man v Fat: The Weight Loss Manual, which grew into an online forum on which male dieters swapped tips and supported one another. (The forum is still thriving and is among the most heartening corners of the internet. If you don’t feel something watching a group of burly dieters cheering on a fellow calorie-counter who has lost his way, swapping tips on getting rid of stretch marks or advising how best to navigate a pending trip to a carvery without ruining his progress, there is something very wrong with you.) But participants were eager for a face-to-face component to their dieting.

“When I was losing weight, I could never understand why something didn’t exist specifically for men,” he says. “I’d tried Weight Watchers and Slimming World but struggled with their approach. Not that they weren’t welcoming but, institutionally, they weren’t suited to me. I was often the only man in the meetings, which wasn’t conducive to opening up about my weight.

A paper published in the journal Obesity Research and Clinical Practice in 2016 found that men and women dieted more successfully in single-sex groups. A study of more than 2,000 people published last year in the journal Diabetes, Obesity and Metabolism also reported that men typically lose weight faster and in greater quantities than women. There are differing attitudes regarding consumption and exercise, too, with men by and large preferring to work out more in order to eat more, while women would rather eat less to avoid lengthy sessions of exercise.

“Culturally,” adds Shanahan, “having a big appetite as a man has historically been seen as a positive thing, whereas for women, that hasn’t been the case. Men and women face different challenges when dieting, and Man v Fat reflects that.”

The first league saw 1,000 men apply for 80 league places, with about 90% of those participants losing weight over the course of the 14-week season. That is a figure Man v Fat has more or less maintained in the three years since launching, with more than 70 leagues now operating all over the UK. The Australian franchise is in its second season, while talks are under way to launch Man v Fat in the US. Players have so far lost a combined 188,000lb. That’s 85 tonnes.

“It’s quite unusual for men to go into any situation admitting some kind of weakness,” says Shanahan. “Being fat is quite a good one because we can all see it. And when we’re in that group, it undoes any machismo around that conversation. With that comes this positivity that you’re all doing it together and it opens up all sorts of conversations you’d never normally have. It’s an odd dynamic, but it’s very empowering.”

Suhal Miah is an immigration officer from north London. He joined Man v Fat in June 2017 weighing 22st 7lb (143kg). He has now almost halved his body weight. Miah says he was always “the fat kid at school”, but his weight shot up after his dad passed away in 2013. “I was suffering from depression and I began constantly eating junk food. I just remember looking in the mirror one day and thinking: ‘What the hell have you done to yourself?’”

Players at the Man v Fat summer tournament in 2018. Photograph: Richard Blaxall

He signed up to the league on the recommendation of a friend, and within two seasons he had lost 4st 10lb (30kg). By far the most motivating factor for him was Man v Fat’s team element. “I don’t like letting people down, and on other diets it’s only yourself that you’re letting down if you don’t stick to it. With Man v Fat, it’s everyone on your team that’s affected if you fail and that helped me stick to my plan.”

As for his mental health, he is in a much better place than he was two years ago. “I was very close to my dad and he died very suddenly, so it came as a real shock. We always had good food together, that was our thing – I think me eating after he died was me trying to connect with him. But I look in the mirror now and I feel so much better about myself. I think my dad would be very proud.”

It’s a familiar story for the Man v Fat coach Michael Falloon. After losing 8st himself in 2016, he qualified as a personal trainer, got a job with Man v Fat and now uses his personal experience and expertise to help others. “Losing weight gave me so much confidence,” he says. “I got to the point where I wouldn’t go to interviews because I thought no one would give someone of my size a job, so I know what the players are going through and the effects being overweight can have.

Matthew Maksimovic is a mental health worker from the outskirts of Cardiff. At 22, he was signed to the Welsh semi-professional team Merthyr Town until a broken leg ended his dreams of playing at such a high level. It was then that he first started suffering from depression and gained weight. He carried on playing, though, until another serious injury a couple of years ago saw him stop playing altogether. His depression worsened and he put on even more weight.

He has now lost 3st 4lb (21kg) since signing up to Man v Fat last May, while his doctor has significantly lowered his antidepressant dosage. In addition, despite being 37, he is playing more football, and at a higher level, than ever before.

“I credit Man v Fat with giving me the belief to play again,” he says. “Losing weight has changed not just my life, but that of my family, too. A day out with my daughter might have been jumping in the car and going to McDonald’s, but now we’ll head out for a walk and play in the park.

“I’m only sorry Man v Fat wasn’t around when I was 22 and I first started struggling with my weight. Who knows what I’d have achieved?”

• To find out about your nearest Man v Fat football league, go to manvfat.com