From smoking 60 cigarettes a day to running 837 miles, Dave Reading is making a huge life change for a good cause.
The father of eight from Dereham first started running marathons in 2014 to maintain a healthier lifestyle.
Now he's in training to run from Land's End to John O'Groats in 2017 to raise awareness for members of the armed forces who suffer from mental health issues, like PTSD.
Part of his decision to take on the fitness challenge was to inspire his big family - his children are ages four to 16 - to get healthy as well.
'I was seriously unfit and thought, I've got all these children, and I really need to sort this out.
'My running has changed all our lives for the better. We work hard on our nutrition and healthy diets these days. We are all so much fitter and happier,' he said.
Mr Reading is an aircraftsman in the Royal Air Force, stationed at RAF Marham.
He decided to raise money specifically for Walking with the Wounded, which is based in Stody near Fakenham, and the Royal Air Force Association after seeing first-hand the mental health toll that combat takes on servicemen and women.
'The planning for this challenge started some time ago. Whilst talking to colleagues I realised what a massive issue PTSD and other mental health issues are in the armed forces. Until recently this hasn't been addressed very well.
'So by undertaking this massive mental and physical challenge I am not only attempting to raise lots of money but also to share awareness of not only the physical sacrifices made by our service personnel but also the health problems that are not visible to the eye,' he said.
To prepare for next year's feat, Mr Reading is doing a practice run on November 5 from Halesworth to Taverham.
Other than raising money for charity, Mr Reading has one last goal for his 2017 run: beating 2006 world record-holder Sharon Gayter's time of 12 days, 16 hours, 22 minutes and three seconds.
To make a donation, go to http://uk.virginmoneygiving.com/dave-reading-SAVMLMBONDS3332016-24379
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