text: what is best to eat before running a half marathon? i've been running to lose weight and now find that i don't know what or how to eat before a long run. congrats on changing your lifestyle.  long runs  10k and longer can be very taxing on the body.  you should start to hydrate with lots of water 7-10 days before the run.  watch your salt intake.  increase your protein intake slightly for a day or so before the race.  on race day, don't starve.  eat complex carbs, a banana, stay away from fats.  most of the time drinks like gatorade contain too many salts depending on the race conditions.  mix it 1/2 and 1/2 with water during the race and have fun.