Losing weight is a challenge, but what if instead of cutting down on food and doing more exercise you jumped in at the deep end and trained to run the London Marathon? Sounds impossible? Meet Hannah Seaman who has lost four stone doing just that. Emma Harrowing reports.

Last spring when Hannah Seaman left her house decked out in jogging gear and trainers she was determined to get fit and lose weight. Her scales in her bathroom were tipping towards the 16 stone mark since she gave birth to her daughter and she longed to feel healthier and have more energy.

All her intentions were good. She had downloaded a running program onto her MP3 player, she had invested in a good pair of trainers and she had psyched herself up to exercise her way to a fitter body.

'The running program said to run for one minute and then walk the next and so on,' says 28-year-old Hannah, a drama teacher at Sprowston High School. 'Having not exercised at all for at least the last six years I couldn't even run for one minute. That first run nearly killed me!'

Like many of us trying to lose weight Hannah joined a weight loss class, which taught her about portion size and healthy eating. Losing weight is never easy and like many who try to cut down on their food intake and try to stick to an exercise regime, Hannah struggled.

'I had always eaten relatively healthily but it was the quantity I was eating that made me pile on the weight,' says Hannah. 'When I was told exactly what size portions I should be eating I realised that I was eating three times as much as I should be.

'It was easy to convince myself that I wasn't overeating as I would tell myself that what I was eating was good for me.'

With her diet under control the next step in any weight loss program is to exercise to burn off fat and tone your body. Many people would sign up to the gym or exercise class and try hard to attend every week. Others would opt to go out running and then struggle to stick to their new jogging routine.

For Hannah, neither was an option. Although on her first attempt at exercise she had struggled to run down the road, her exercise plan was on a much grander scale; she was going to train to run the London Marathon.

Says Hannah: 'After watching last year's London Marathon I was inspired to get off the couch and run it myself in 2011.

'There are many reasons why I want to run the marathon. The first is to achieve my goal to lose weight and get in shape and the second is to raise money for the charity Ataxia UK in honour of my step-dad John who lived with Friedreich's Ataxia and died when I was 16.'

Ataxia is a condition that affects balance and coordination resulting in symptoms such as slurred speech, tremors or shaking, and in some cases causes problems with walking. Some sufferers can fully recover from the disease but in many cases, including John's, Ataxia can get worse over time.

'John was in a wheelchair in his teens and his condition got progressively worse until he died from a heart attack,' says Hannah. 'Despite his condition he led a very active life, building a specially made canoe so that he could take part in water sports and travelling the world in his wheelchair were two of his achievements.

'His courage and motivation despite his illness has given me the determination to not only lose weight and get fit but to achieve something beyond that – like running a marathon.'

Hannah has progressed from being unable to run for one minute 16 months ago to running 18 miles in one session. Her training involves doing two short runs in the week and a long run at the weekend.

'The main hurdle when doing any exercise is not to listen to your inner voice when it tells you to stop,' says Hannah. 'It's easy to talk yourself out of going for a run and it's easy to let your thoughts convince you that you can stop running as soon as it gets a little tough. I've had many arguments with myself while running, but all I do is picture my step dad and my daughter and I instantly get the motivation I need to complete a session.'

One of the excuses Hannah could use not to go out running is that she needs to look after her 18-month daughter Delphi Leavold, left, when childcare isn't available, but Hannah is so determined to achieve her goal that she has set up a treadmill in her house so that on the days she has to look after her daughter she can run on the treadmill instead.

Hannah's commitment has paid off as her fitness levels have soared and she has lost four stone in weight. She also took part in the Norwich half marathon last month but a pulled hamstring prevented her from completing the run, a situation she hopes not to be in when she runs the marathon on April 17.

'I know running the marathon will be tough and painful, but I only plan to do this once in my life,' says Hannah.

'My family and friends have all chosen a song for a playlist for my MP3 player so that I can listen to the songs they have selected while I run. I think this will give me the motivation to keep going and achieve my goal in running the London marathon.'

Many diet and fitness regimes fail as soon as you reach your goal and revert back to your old way of eating and exercising. Hannah aims to prevent herself slipping back into her old habits by continuously setting fitness goals so that she always has something to work towards.

'I'm not planning to train for something as big as the marathon but I have signed up for Race for Life on May 14 and 15 to give me something else to run for,' says Hannah. 'If I didn't set myself goals I know that I would quickly slip back into my old ways of not exercising and eating far too much.'

You can sponsor Hannah at www.justgiving.com/hannah2011

Find out how you can get fit at one of Norwich's newest fitness classes on the Life Matters pages in tomorrow's (Friday April 15) Norwich Evening News.