So, I think I have told you all in my bio that I was an avid triathlete for over 18 give or take a year..... I have done 5 marathons and several half marathons.
I have been injured for a while and had to take 5 months off and now can only run between 3-4 miles which I will take because I love running.
The best foods to eat before running and you should eat about 1 hour before hand. I do best with whole grain toast and a touch of peanut butter, oatmeal or a banana. I will not suggest eating citrus fruits before running. Somehow it just comes up and makes for a nasty stomach ache.
Also, if you are thinking of doing a marathon and have never done one before, start slowly. Start with a 5K, then a 10K, then a half marathon and then a full. Training for a marathon takes time and so much effort. Be good to your body!