What you eat before a long run matters more than most runners assume, and less complicated than most guides make it sound. The short version: eat a carbohydrate-heavy meal 3 to 4 hours out, keep it low in fat and fibre, and add a small top-up 30 to 60 minutes before if you need it. Getting this timing right protects both your energy and your stomach.
Why does pre-run timing matter so much?
Digestion and running compete for the same resources. When you eat, blood flow shifts toward your gut to help break food down. When you run, blood flow shifts toward your working muscles. Eat too close to a long run and you're asking your body to do both at once, which is a common reason runners feel sluggish or nauseous in the first few kilometres.
Giving yourself 3 to 4 hours before a longer effort lets a proper meal mostly clear your stomach while still topping up glycogen stores in your muscles and liver. That window isn't arbitrary. It's roughly how long it takes a mixed meal to move through digestion enough that it won't be sitting heavy when you start moving.
What should the 3 to 4 hour meal look like?
This is your main fuelling meal, and it should lean heavily toward carbohydrate, with moderate protein and comparatively little fat or fibre. Fat slows digestion, and fibre, while great for general health, can trigger bloating or urgency mid-run if eaten too close to exercise.
Good options include:
- Rice with lean chicken or eggs
- Toast with honey or jam and a banana
- Oats made with milk, topped with banana, with the high-fibre extras like nuts and seeds kept light or skipped
- A bagel with a thin spread of peanut butter and honey
Portion size should feel like a normal, satisfying meal rather than a feast. Overeating, even of the right foods, close to a long run can leave you feeling heavy regardless of what's on the plate.
What about the 30 to 60 minute top-up?
Closer to run time, smaller and simpler is the rule. This isn't a second meal, it's a small addition to keep blood sugar topped up right before you start. A banana, a few dates, a slice of toast with honey, or half an energy gel all work well here.
Fibre and fat should be almost absent at this point. This is not the moment for a big bowl of muesli with nuts, or anything creamy or fried. The goal is fast, simple carbohydrate that sits quietly until you're moving.
Some runners skip this step entirely and are fine on the 3 to 4 hour meal alone. Others, especially on longer runs starting first thing in the morning after an overnight fast, find the top-up makes a noticeable difference to how they feel in the first 30 minutes.
Why does protecting your gut matter on long runs?
Exercise itself changes how your gut behaves, independent of what you eat. Sustained running redirects blood flow away from the digestive system toward working muscles, and the mechanical jostling of running adds further stress on top. Together, these can bring on nausea, cramping, bloating or an urgent need for a bathroom, a cluster of symptoms researchers group under exercise-induced gastrointestinal syndrome (Costa et al., 2017).
Food choices before a run don't cause this syndrome, but they can make it noticeably worse or better. High-fat and high-fibre foods slow gastric emptying and leave more material sitting in the gut while blood flow is being diverted elsewhere, which is exactly the wrong combination on a long run. Sticking to low-fibre, low-fat, carbohydrate-forward food in the hours beforehand reduces the load your gut has to deal with while you're also asking it to cope with the stress of running.
This is also why "eat clean" advice from general nutrition doesn't always translate well to pre-run eating. A big salad with nuts, seeds and avocado is excellent nutrition on a rest day and a rough idea 90 minutes before a 25 km run.
How do you figure out what actually works for you?
Every runner's gut responds a little differently, which means the only reliable way to find your pre-run routine is to practise it, not read about it. Trial your meal timing, portion sizes and specific foods on training long runs, not on race morning. If a food causes trouble, note it down and try something else next time.
This same logic applies to fuelling once the run starts. If your long runs regularly pass 75 to 90 minutes, that's the point where carbohydrate during the run starts to matter alongside what you ate beforehand. Testing a gel on a Sunday long run, at the pace and effort you'll actually race or train at, tells you far more than testing it for the first time under race-day nerves. Sunday Salt's gels are built to be gut-friendly by design: a maple syrup base with a natural glucose and fructose mix, no maltodextrin, and nothing artificial, which matters when your stomach is already dealing with the stress of a long effort.
What are good go-to pre-run meals to start with?
If you're not sure where to start, these combinations are a reasonable default for most runners heading into a long run:
- 3 to 4 hours before: porridge with banana and honey, or rice with chicken and a small amount of soy sauce
- 60 minutes before: a slice of white toast with jam
- 30 minutes before, if needed: a few dates or a small banana
None of these are exotic, and that's the point. Long-run nutrition rewards boring, familiar, well-tested food over anything novel or "optimised."
Frequently asked questions
Can I run on an empty stomach? For a short, easy run, yes, most people manage fine. For a genuinely long run, running fasted increases the risk of low energy and poor performance, since you're starting without topping up glycogen. A small carbohydrate snack beforehand is usually worth it once the run gets long.
What if I only have 30 minutes before my run? Skip the big meal and go straight for something small and simple: a banana, a few dates, or a small handful of dried fruit. Save the bigger, more filling meal for a day when you have more time before heading out.
Is coffee okay before a long run? For most runners, yes, and it may even help alertness and perceived effort. The caveat is gut sensitivity. If coffee tends to send you straight to the bathroom, test your usual pre-run coffee habit on a training run well before relying on it before a race.
Should I avoid dairy before a long run? Not necessarily, but some runners find dairy harder to digest under the stress of running, even if it's fine any other time. If you're prone to GI issues, it's worth testing a dairy-free version of your usual pre-run meal to see if it makes a difference.
References
- Costa, R. J. S., Snipe, R. M. J., Kitic, C. M., & Gibson, P. R. (2017). Systematic review: exercise-induced gastrointestinal syndrome. Alimentary Pharmacology & Therapeutics, 46(3), 246-265.
- Jeukendrup, A. E. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 44(Suppl 1), S25-S33.
Olly. Sunday Salt.
