Three plus-size women say they are living proof you don't have to be thin to be healthy.

Alix McKillop, 43, from Bristol, Julie Creffield, 37, from East London, and Zoe Davies, 34, from Derby all consider themselves to be fit and active.

Between them, they run marathons, compete in Ironman competitions and teach others how to get fit.

However, rather than svelte size 10s, their weight ranges from 14 stone up to 20 stone. Here, they explain why they believe when it comes to fitness, they believe size doesn't matter.

Zoe Davies, a 34-year-old veterinary nurse from Derby weighs 19 stone – but is a qualified fitness instructor and completed the Great North Run this September

Julie Creffield, 37, from Stratford in east London, pictured here alongside long-distance runner Paula Radcliffe, is a size 18 and runs marathons

Alix McKillop, a 43-year-old chef from Bristol, started exercising for the first time just over two years ago. he weighs over 14 stone – and is due to complete a full Ironman triathlon race later this year

ALIX MCKILLOP, 43, 14 STONE IRONMAN COMPETITOR

Alix McKillop, a 43-year-old chef from Bristol, started exercising for the first time just over two years ago. She weighs over 14 stone – and is due to complete a full Ironman triathlon race later this year.

She said: 'I’ve struggled with my weight all my life and did very little exercise up until a few years ago. I do remember going on one skiing holiday just before my 40th birthday with my husband David and some of his friends where they all went out onto the slopes, leaving me stuck on the sofa in the hotel.

'I just didn’t think any kind of sport or exercise was for me. I was so big and unfit it was so much effort to do any kind of exercise, and dragging myself up and down streets on my own in an attempt to run wasn’t something I’d ever want to do. It was always easier to shut myself inside than to go through that ordeal.

'My daughter Laura, who’s 23 now, had run a couple of half marathons and told me how much she enjoyed it, and I always had a burning ambition to run the London Marathon, having watched it on telly religiously as a girl.

'So shortly after my 40th birthday I decided enough was enough and signed up for sessions with a personal trainer at a local gym. My primary motivation to get fit was never to lose weight – despite regularly pushing 20 stone – but to simply have more energy and strength, to feel more enabled.

Alix said she was so big and unfit it was so much effort to do any kind of exercise, and would instead shut herself indoors

But shortly after her 40th birthday Alix - right - signed up for sessions with a personal trainer at a local gym

Alix hasn't looked back since and finished the London Marathon in five hours

'I entered a blogging competition at the gym, where you charted your progress, which really motivated me.

'The first few weeks were incredibly hard, but I stuck at it, and quickly developed cardiovascular fitness and strength. I did drop a few pounds, but I also wanted to eat healthily to keep my energy up for my exercise.'

After about six months of gym work, she joined a running club in October 2014 which she said was 'the best decision she ever made' despite it being a scary experience.

She said: 'Everyone was so supportive, cheering me and the other slow runners across the finishing lines whenever we did a run, giving us tips and being so incredibly friendly.

'When you’re stuck at home you think the only option is plodding around the streets on your own, not knowing there are these fantastic running communities out there.

Alix had regularly weighed more than 20 stone before she took up exercise, and is set to compete in the Ironman triathlon later this year

'I signed up for a duathlon, then a 20k cycle and then a 5k run, then got accepted to run the London Marathon, which had always been a dream of mine.

'During training for that I ran three 10k races and the Bath Half Marathon. I finished the London Marathon in five hours, which I was thrilled with.

'Over last summer I ran three more 10ks and five triathlons, even coming second in one. I actually won a ‘Go Tri’ duathlon.

'I’ve got two half Ironman triathlons and a full distance Ironman lined up this year – a 2.4km swim, 112km cycle and then a full marathon. It’s obvious I love a challenge!'

Although she has lost six stone, Alix still struggles with her weight - but still feels fit and healthy.

She said: 'I love my exercise and the whole community I’m part of now. It’s not about the weight, it’s about doing what you enjoy, feeling full of life and energy. I can’t believe I spent so many years worried what people would think if they saw a fat woman running.

'I can’t urge other oversized people enough to just get out the door, join a running club and see how great life can be. Don’t sit on the sofa worrying about what anyone else thinks or if you’re good enough.'

JULIE CREFFIELD, 37, SIZE 18 MARATHON RUNNER

Julie Creffield, 37, from Stratford in east London, is a size 18 and runs marathons.

Julie Creffield, 37, from Stratford in east London, is a size 18 and runs marathons

When Julie Creffield - pictured - was working on the Olympic project near her home she entered a 3km run, during which a young boy shouted 'Run Fatty Run'

Although it hurt, the insult was to be the inspiration behind Julie Creffield's transformation which sees her regularly compete in races

She said: 'During my late teens and early 20s I have to say I was enjoying life a bit too much without ever thinking about my health. By 23 I was 20 stone, I often ate fast food, never exercised and regularly had big drinking sessions with friends.

'I was working on the Olympic project at the time and felt I had to make an effort with my health, so entered a 3km run. With absolutely no training I almost died on the way round, but nothing hurt more than a young boy shouting “Run Fatty Run”.'

In that moment, she became determined to take control of her life.

'The next day I signed up for the London Triathlon, which I completed three months later in an XL wetsuit that just about fitted my size 18 body.

Julie (pictured here before she started her fitness regime) went onto set up a website called The Fat Girls’ Guide to Running which gives tips on how to start getting fit

She is still a size 18 and 'still loving every aspect' of her life. Julie said: 'I know there are associations with being big and being unhealthy, but I eat healthily, I love exercising and I love being me'

'I carried on doing as much exercise as I could over the next few years, but my focus was as much on health as losing weight – I rarely drink alcohol now and with advice from a nutritionist I have a really balanced, healthy diet. I became a mum in January 2013 and don’t want to pass on any bad habits to my daughter Rose.'

She continued: 'Because I do love exercise so much and I also hate the idea that anyone should be told they’re too big to exercise, five years ago I set up The Fat Girls’ Guide to Running website which gives tips on how to start running if you’re larger or a mother, nutrition tips, events, a kit guide and a forum so you never feel alone.

'The website got over 10,000 hits in just a few weeks and I realised how many people there are out there like me. The approach is Health At Every Size – or HAES – so you don’t have to feel that because you’re big you might as well throw it all away by stuffing in unhealthy food on the sofa. We all know slim doesn’t equal fit and fat doesn’t equal unhealthy.'

In 2014, Julie claims her GP told her she was too big to run 26 miles, despite the fact she had already done the London Marathon two years before.

'I took that as challenge and completed The Brighton Marathon just three weeks later, along with numerous other races in the upcoming months', she said. 'It’s all about taking part, feeling inspired and enjoying it at your own level. Weight loss isn’t my goal, it’s about being happy and healthy.

We all know slim doesn’t equal fit and fat doesn’t equal unhealthy

'I’ve been contacted by women who say they used to run on a treadmill in their shed they were so frightened of being seen exercising. How can any doctor say you’re too big to exercise? It’s outrageous.

'I’m still a size 18 and still loving every aspect of my life. I know there are associations with being big and being unhealthy, but I eat healthily, I love exercising and I love being me. We’ve had over 500,000 hits on the website this year alone and hoping to make it even bigger and better in 2016.

'I have a new book out called New Year, Same You – Health and Happiness at the Size You Are – it encourages people to ditch the idea of New Year resolutions and live every day to the full.

'How dare any scientists try to tell overweight people they can’t be fit? They need to speak to the hundreds of thousands of overweight people I’ve had contact with in the last few years to ask them how they’re feeling, to see the massive health benefits they’ve seen from taking up exercise.

'Of course I haven’t tracked overweight people through old age, so I don’t know when they might die compared to if they’d never exercised, but it seems craziness to send out any message to anyone saying that exercise isn’t the absolute panacea that it we all know it can be.'

Julie's book is available to buy here.

ZOE DAVIES, 34, 19 STONE FITNESS INSTRUCTOR

Zoe Davies, a 34-year-old veterinary nurse from Derby weighs 19 stone – but is a qualified fitness instructor and completed the Great North Run this September.

She said: 'I’ve struggled since I can remember with my weight – being large was a taboo subject when I was young. You were just called "fat" and left on a shelf.

Zoe Davies, a 34-year-old veterinary nurse from Derby weighs 19 stone – but is a qualified fitness instructor and completed the Great North Run in September

'The last thing anyone ever expected me to do – least of all me – was exercise. The inference was that plus-sized women were stupid and had no self control, that we chain-smoked and stuffed cakes in our faces our day.

'My turnaround happened just over three years ago when I was sitting in the pub with friends and decided I was sick of feeling like I couldn’t exercise, that I wasn’t allowed to enjoy that part of life which other people did.

'I weighed 22 stone then and knew I was too big, but that was only part of the equation – I knew that I wanted to be healthy. I asked my husband Ian for personal training classes for Christmas, and I have to say it was hard, but I loved it. I felt happier, I slept better, and of course over time I lost some weight.

'The hardest part for anyone plus-sized is the first step, being brave enough to admit that you want help, feeling like people are going to laugh at you.

Zoe's turnaround happened just over three years ago when she was sitting in the pub with friends and decided she was sick of feeling like she couldn’t exercise

With the help of a personal trainer Zoe - left - realised she didn’t have anything to be ashamed of, and that there were countless people like her in that gym who didn’t look stick-thin

Zoe enjoyed exercising so much - going to the gym or running seven times a week - that she went to night school and trained as a gym and then a boxercise instructor

'But with the help of that personal trainer I realised I didn’t have anything to be ashamed of, that there were countless people like me in that gym who didn’t look stick-thin but who were really happy exercising on their own level.

'In fact, I’d say there was a real community of over-sized gym goers who supported each other, which was a fantastic feeling.'

Zoe enjoyed exercising so much - going to the gym or running seven times a week - that she went to night school and trained as a gym and then a boxercise instructor.

'I’d see large ladies turn up all shy and retiring and within a few weeks they’d be throwing punches with massive smiles on their faces', she said. 'I’m hoping that me being big helped them get over their fears.

'Sometimes when I’d be out running people would say cruel things, but you’re always surprised at some reactions – one young lad ran past me when I was out jogging, turned to face me as I was doing a walking section and held out his hands to encourage me to keep going.

'So not everybody wants to see overweight exercisers fail or ridicule them.

'I did the Great North Run this September and have to say the atmosphere there was possibly the best I’ve ever experienced anywhere in my life, the buzz I got from all the supporters.

'And there was every possible size and shape there, which is how it should be. I’ve signed up for the next three Great North Runs already!

'I’ve been down to 18 stone, and I’m now 19 stone and a size 22. Of course I know I could and perhaps should be slimmer, but I eat healthily and I know I’m probably in better shape than those people in the chip shop smoking their fags who jeer at me as I run past, uphill.

'Nobody’s ever going to tell me to stop exercising.

'This new Swedish study is very negative and I don’t think does anyone any favours – if you’re slim and chain smoke or eat like a rabbit you think it’s okay not to exercise, and if you’re overweight you think, why bother getting into shape?'