Trying to learn what and when to eat on the run can be a little overwhelming. For a start the advice that's out there is often confusing, not to mention contradictory. With one person touting the benefits of running everything fasted and another swearing if you don't pound a sugary gel every 20 minutes you will collapse in a heap and maybe die.
But it really doesn't need to be that complicated, with a few basic guidelines and a little trail and error you can work out what works best for you in no time.
Whatever you eat should tick these three boxes
Find a few foods that fit that list and now all you need to do is experiment (in training) with them and see what works best. Don't worry about whether it's traditional running food or about the carbs/calories just yet, focus on what works for you. Once you've found something that works, then you can start tweaking the amounts for each run.
Fuel up before you head out the door and not only will you feel/perform better but you may not even need to refuel on the run (depending on the distance). It doesn't need to be anything too complicated either; an apple, a slice of toast & honey or my favourite a small bowl of porridge 60 - 90 minutes before you run will do the trick. Aim for roughly 150 calories, see how you feel and adjust from there. More on what to eat pre run here
If you've eaten pre run, just take some water out with you, especially if it's hot but no need to worry about refuelling.
Once you start going over 60 minutes, you'll want to top up those energy stores with some carbs and some calories on the move. Start off with about 150 calories and up to 20g of carbs eaten at the hour mark and see how you feel. Don't forget to sip some water as needed too, especially after eating.
When you're out for 2 hours or longer on those later marathon training sessions, you'll need to refuel more than once. Starting at the 30 to 45 minute mark, take on between 100 - 150 calories with 15 - 20 grams of carbohydrates. Repeat every 45 minutes for the duration of the run. Again if you feel hungry or over faced, just change up the numbers slightly till you hit a sweet spot.
Best practice is to refuel for all efforts over 90 minutes, think half marathons and further, but it's often best to avoid it for anything shorter. For those sub 90 minute runs try and see what works for you, experiment with both a small snack mid run or a slightly bigger pre run meal before hand.
For marathons, ultras or any other long event, you typically want to be taking on between 100 to 200 calories with 20 to 50 grams of carbs per hour, every hour that you are out there.
When it comes to those really long runs though, the ones that creep well past the six hour mark, you might benefit from eating a 'meal' too. At some point your body and mind will want more than just those little 100 calorie snacks. Regardless of what you're fuelling strategy has been so far, try and get some real food down you at this point; a sandwich, soup, a little bit of pasta or whatever they have at the checkpoint (if racing). It will help a lot.
Remember though this all just guidelines, the only way to really know what works best for you is through lots and lots of trail and error. Fortunately that means plenty of excuses to get out and go running.