What you eat before running can affect your energy, comfort, and performance. Eat too little and you may feel tired halfway through your run. Eat too much—or choose the wrong foods—and you could end up running with a heavy stomach.

The good news is that pre-run nutrition does not need to be complicated. For most runners, the goal is simple: give your body useful energy without upsetting your stomach.

Your body stores carbohydrates as glycogen in your muscles and liver. During running, especially at moderate or higher intensities, carbohydrates are an important source of energy.

If you haven't eaten for many hours, you may still be able to complete an easy run, but harder or longer sessions can feel more difficult.

Eating beforehand can be particularly helpful before longer runs, races, interval sessions, or workouts where you want to perform well.

However, more food doesn't necessarily mean more energy.

Running shortly after a large meal can cause bloating, cramping, nausea, or the uncomfortable feeling of food moving around in your stomach.

Timing depends on how much you eat.

If you're having a normal meal, giving yourself roughly two to four hours before running is a practical starting point.

If you're running sooner, choose a smaller snack that is easier to digest.

For example, before a morning run you might have:

You don't need all of these. One simple option may be enough.

The closer you are to your run, the smaller and simpler your food generally should be.

Carbohydrates often make a good pre-run choice because your body can use them as fuel during exercise.

Foods such as bread, rice, oats, cereal, fruit, and pasta can all contribute carbohydrates.

Before a long run, a meal containing carbohydrates along with some protein can work well. For example, you might have oats with yoghurt and fruit or rice with a moderate serving of protein several hours beforehand.

You don't need a special "runner's food."

Normal everyday foods can work perfectly well.

Healthy foods aren't automatically ideal immediately before running.

Large amounts of fat, protein, or fibre can take longer to digest. For some runners, eating too much of them shortly before exercise causes stomach discomfort.

That doesn't mean you should remove these nutrients from your diet. They are important parts of good nutrition.

It's mainly about timing.

A large spicy meal, fried food, or a very high-fibre meal shortly before a hard run may not be the best experiment.

Not necessarily.

Some people comfortably complete short, easy morning runs before breakfast. Others feel weak, hungry, or light-headed without eating.

There isn't one rule that works for everyone.

If you're doing a short easy run and feel good without breakfast, you may not need to force yourself to eat.

For longer or demanding training, eating beforehand can become more useful.

If you frequently feel dizzy, unusually weak, or unwell while exercising, don't simply assume that running without breakfast is the only cause. Stop exercising if necessary and discuss recurring symptoms with a healthcare professional.

Your stomach needs training too.

If you're preparing for a race, test different foods during your normal training weeks.

Find out what food works, how much you can comfortably eat, and how long you need between eating and running.

Race morning is not the time to suddenly try a giant breakfast, unfamiliar energy product, or new sports drink because another runner recommended it.

Use what you already know works for you.

Pre-run food should help your running—not make it more complicated.

For longer or harder runs, carbohydrates can provide useful fuel. Allow more digestion time after larger meals and choose smaller, simpler foods when you're running soon after eating.

Most importantly, pay attention to your own body.

Your perfect pre-run breakfast might be another runner's stomach disaster.

Experiment during training, keep your routine simple, and build a strategy that gives you energy while keeping your stomach comfortable.