Assuming you have training plan of some sorts leading you on the way to a marathon your next task is getting used to eating, or as you should think of it Fueling your run. While the obvious may seem to be right in front of you that you can eat some food, drink the latest sports drink and run like a champ this is only true to a point for most of us and usually only on shorter training runs.
As you run further distances you will start pushing the limits of a few parts of physiology, all of which are predictable and manageable provided your fueling your run properly and figured out your unique tolerances for fuel. As you run and start to push the 2 hour mark of physical activity you will have depleted the glycogen (stored energy) that largely fuels your muscles during physical activity and you need to be replacing / augmenting it to keep going.
Your first marathon is going to be much longer then 2 hours (4-5 in many cases) this is why you need to be taking in about 200 calories an hour of “Fuel” made up of the liquid and food you will will need to keep on running after around 2 hours and give your body the calories it needs to function and start using your fat as a fuel source for going long distances on foot.
This like your running takes practice. Practice in the sense you need to find what foods you can tolerate eating, and when you need it. The tolerating part of things is the first step. There are a number of running fuel products on the market, some at the grocery store, some at the specialty sport stores and I recommend that you try a wide variety when you are out on runs around 10-15K starting out to see what ones you can handle eating at around half way through a run then every 20-30 minutes there after.
This is because when you are running you are diverting blood from your digestive system that is normally needed to digest food as it’s flowing to your legs and major muscle groups to keep you going. What this means to selecting food sources is food that may be fine for you to eat normally may be harder or impossible for you to digest easily while running ultimately leading to a run cut short by GI distress as food sloshes in your stomach leaving you walking to the nearest washroom.
In my experience I had a lot of issues digesting what I assumed would be the right things to eat and drink including some specialized race gels etc. I found through trial and error different training products that worked for me and with a reoccurring theme of the more natural the food the more easily I digested it during intense short runs or 3 hour long runs.
To this end I recommend products like eload or other natural gels for the simple natural sugars and electrolytes you need and to try natural solid food based products like EnergyBits, Clif Bars etc with plenty of water to keep yourself hydrated washing it all down.
WHAT YOU EAT WHEN NOT RUNNING: PRE-RUN & RECOVERY MEALS
What you eat before and after your runs is also key. To avoid the same GI problems you get from eating on the run you need to make sure you leave enough time to digest food you eat before heading out on a run to avoid GI issues.
The time and what foods may aggravate your stomach (dairy, spicy etc) varies person to person, but smaller meals of simple natural / whole foods low in fiber about a half hour to hour before seems to be the right idea for most.
Once your run is over you need to get some good quality fuel in to your body to replenish and build the muscles you used during your run. I recommend grabbing a banana or other hand fruit when you walk in the door. Get cleaned up and then eat a balanced meal asap with protein and carbohydrates, drink lots of water to rehydrate etc. This ensures you don’t waste the training benefit of your run by not fueling your body / muscles to repair and improve.
While the common myth is with all the miles you are putting on your legs you can eat just about anything this is not really true. If you want to see real gains from your mileage and fitness don’t overdo things portion wise post run and make sure what you do eat is clean and healthy as possible even throwing in a recovery drink like Vega sport recover to aid recovery etc.