A woman who tipped the scales at almost 20st has shed nearly half her body weight after she was forced to stand during an 11-hour flight - because she feared she was crushing the woman in the seat next to her. Sharon Smith, 43, from Halesowen, West Midlands, was a bulky size 26 when she went on the business trip in December 2012 and struggled to fit in the plane seat. Today she weighs in at a healthy 9st 9lb and is due to run a 10k race on Sunday, when two years she would have struggled to walk half a mile, let alone run six. Scroll down for video . Sharon Smith shed almost half her body weight after she decided to take up running . Sharon said she lost 4st through joining a slimming club but then shed another four-and-a-half stone after taking up her sporty hobby. Her weight loss began just under two years ago when she joined Weight Watchers Online, but did not weigh herself immediately. After six months of following the plan, she was 18st 6lb so estimates that when she started she was 'way over 20st' and a size 26. She said that although she had always been larger she had never been happy being overweight. Sharon said: 'I was never one of those people who was okay being big, it had always upset me but my head wasn't in the right place to do anything about it because I had a busy working life.' She put her unhealthy lifestyle down to commuting to London for her job as a children's clothes designer for Aquascutum which saw her do minimal exercise. At her heaviest Sharon was over 20st and a size 26 but she has now slimmed down to 9st 9lbs and is a size 10 . But the turning point came for Sharon after having to 'squeeze' her bulky frame into seats on trains and planes. 'I started commuting to London in August 2012 and the business trip to Hong Kong was in December that year,' she said. 'I had been travelling out there for ten years but luckily I had always managed to upgrade or have no one in the seat next to me. 'But this trip coming back I was in economy and it is the one that really sticks out in my memory. 'I remember being rammed in my seat with a lady next to me. I felt uncomfortable not just for me but for her too. Sharon says her weight was down to to commuting to London for her job as a clothes designer but after quitting her job to go freelance and work from home, Sharon was able to exercise at lunch . 'I ended up standing for the entire flight with my iPod in. 'I was genuinely worried I might hurt the woman in the next seat because of my weight. She didn't say anything but I just didn't think it fair for her to suffer because of my size. 'The flight attendant even offered me the seats they use for take-off and landing. But with the big long-haul jets there is more room to stand.' But even back in the UK, she was fed-up of the daily humiliation of her long journeys to work. She said; 'On top of this, every time I went to London I was fed up having to squeeze into train seats.' Sharon made small changes to her lifestyle, such as walking around London rather than taking the Tube, and in January 2014, she decided to quit her high-flying job and go freelance. She began working from her home which meant she could go for a walk every lunchtime. Sharon took up running last March and by now was around 13st to 14st and finding it difficult to lose any more weight. Friends were talking about the 'Couch to 5k' beginners running programme so she started doing that and signed up for a 5k Race for Life, which she did last July in an impressive 40 minutes. After getting a taste for activity Sharon joined a runners' website, The Running Bug, which 'changed her life' as she was egged on by other enthusiasts. Sharon added: 'The site, especially the members' forum, gave me so many tips and so much encouragement.' Sharon took part in a 5k Race for Life which she completed in just 40 minutes . The designer has since completed two 10k runs last year and even ran the Brighton half marathon in two hours and 59 seconds in February this year. Sharon, who is also running the Morrisons Great Birmingham 10k run this Sunday, added: 'The weight loss really picked up when I started running, it really helped with the momentum. 'Once I started training for my first 10k race last summer, the pounds really dropped off. 'I think it was a mix of things that caused the problems, I knew my diet wasn't healthy. 'At the weekends I tended to graze the whole day through so there wouldn't be that many minutes when I wasn't eating, it was constantly chocolate and crisps. 'Now I don't buy any processed foods, I don't even buy ready-made bread and I try to make everything from scratch. 'I eat a lot more fruit and veg and try to eat health fats like nuts.'
Children's clothes designer Sharon Smith, 43, weighed over 20st .
Joined a slimming club, then took up running to shift the pounds .
Now a 9st 9lb size ten and has run two 10ks and a half marathon .