What to eat the morning of a long run

The two ways to get this wrong are opposite and equally miserable. The first is eating nothing, which works fine right up until the run gets long enough that it doesn't. The second is eating something ambitious — leftover pasta, a smoothie with seventeen ingredients, an entire breakfast buffet — and you may discover somewhere around mile 10 that your gut has developed strong feelings about the decision.

For most of my running life I was firmly in the “no breakfast” camp, mainly because I am not a morning person and eating before 7am felt like an insult on top of an injury. And to be fair: fasted running is fine for shorter efforts. 

For anything under an hour, your glycogen stores are more than sufficient. There's legitimate research suggesting habitual fasted training nudges the body to burn fat more efficiently over time, though it found no difference in overall performance between fasted and fed groups, so it's an adaptation rather than a shortcut.

What to actually eat

The pre-run breakfast needs to satisfy exactly one criterion: it should clear your stomach before your gut loses its blood supply. Everything follows from that.

• High in simple carbohydrate. Simple carbs like white bread, white rice and banana digest fast, clear the stomach quickly, and convert to available glucose without requiring much from a gut that's about to be significantly deprioritised.
• Low in fat. A cheesy or buttery breakfast will still be sitting in your gut long after you've started running. There is a reason this is bullet number two.
• Low in fibre. High-fibre is an excellent choice most of the time, but before a run it is capable of causing genuine logistical problems when your gut is compromised and the nearest toilet is four miles away.
• Low in protein. Protein takes longer to digest than carbohydrate, demands more from the gut, and does nothing useful for a run you're about to start. At almost every other meal, eating more protein is the right call, but this is the one occasion where the recovery shake can wait.

How long to leave it

Even the right food causes problems if it's still in your stomach when you leave.

The general guidance is 2–3 hours for a proper meal, 30–60 minutes for something small. A banana eaten fairly close to the start is usually fine. Two slices of toast with jam and a glass of juice wants at least an hour, probably more.

The only way to find your limit is to test it — some people can eat 30 minutes out without issue. Others need two and a half hours before anything resembling normal function resumes. I highly recommend starting conservative and work backwards, and plan your routes around available toilets when you are experimenting.

Race morning is not the time to find out

All of this applies on race day, with one additional rule: don't experiment. Whatever has worked before long runs in training is what you eat before the race. The hotel breakfast buffet is not the moment to try something new. Interesting choices at 6am have ended more marathons than bad training.