As a dietitian I work a lot with marathon runners, especially around the Cork and Dublin Marathon in Ireland. One of my success stories involves a marathon runner who was struggling to improve his race time and was experiencing frequent fatigue during runs with stomach discomfort. A lot of the time athletes will under-fuel and not consume enough carbs. As well as the incorrect type which causes stomach discomfort during running. We provided him with guidance on pre, during and post marathon nutrition. With about 3 months of practice with carbohydrates and fuelling he was able to shave above 20 mins off his time and was pain free.