In reply to katyc:
Also dont try to lose weight during marathon training.. you will normally anyway, but if you want to lose weight do it at other periods of your season.. not during marathon training.
I'd ignore specific diet advice on types of food.. you need to work that out yourself, when to eat, breakfast before long runs, food during the day is so person specific its pretty useless and confusing.
I run with a few who dont eat breakfast before 16 mile runs on a sunday at low 6 pace.. I have to get up and have P&J on toast a good few hours before, we're all set up differently and you aren't going to change your digestive system and physiology in the 8-10 weeks before a key race.
If before a long run I feel hungry I'd certainly eat, it needs to be quality and enjoyable or you won't do the miles, so a nutella sandwich, even just a few spoonfuls of nutella.. you dont run long runs in marathon to lower your weight, its to improve your aerobic efficiency.
Fruit will cause severe in bloating in some, some it's gods gift, if I touch an apple I'm in a mess, yet banana's are great.