GO EASY ON FAT
For long events, such as marathons, your body turns to fat for energy when carbohydrate sources run low.
Most athletes get all the fat they need by following the basic dietary guideline to eat mostly unsaturated fat from foods such as nuts, avocados, olives, vegetable oils, and fatty fish like salmon and tuna.
Avoid fatty foods on the day of an event, since they can upset your stomach.