Racing and training are very different. I don’t take water or gels on training runs up to and including 20 miles, unless the weather is hot. If it is then I will take water only in a belt. I wore the belt in a race once and it was like carrying a brick – never again, that's what drinks stations are for. In a half marathon race I take a cup of water once, about midway, walking through the drinks station as it costs almost no time and ensures you get hydrated, no gels. In a marathon I take regular gels at miles 5, 10 and 15 and one with caffeine at mile 20. Energy conservation and hence early fuel is more important at this distance. Water at 6 miles, 12 miles, 15 miles, 18 miles and 21 miles (or as near as possible). I wouldn’t get hung up on taking gels/ fuel for training, although you should try it out once or twice to make sure it doesn’t make you sick (or worse).
Should also add I use 'Gu' gels now as they are lighter (less water) than 'SiS' which was what I used previously, but each to their own on this really.
Edited: 26/04/2012 at 16:44