I find my body tells me in no uncertain terms when I'm not eating enough to fuel my running - and for me that means not enough wholegrain bread, cereals etc. Maybe its to do with running as opposed to strength training but too few carbs and a more protein based diet just depletes me totally. Of course I eat enough protein, but I need my carbs too.

My runs start to feel like I'm running through water. Every now and then I'll have a run like that anyway, but when it starts to feel awful every time, its a sure sign to improve my diet. (I tend to get lazy with my eating and not eat meals, but just pick all day. When I do that, i stop eating bread, cereal etc, and eat more crappy foods - biscuits, chips, too many cappucinos...)

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Jacqui