Running guides

What to eat before a run: timing, carbs and the research

The ISSN position stand says carbohydrate-rich snacks or meals are commonly recommended in the hours before longer, harder exercise. For shorter exercise, a meta-analysis found no performance benefit from eating first.

By RunFast · Updated 15 October 2026 · 9 min read

What to eat before a run depends on the run. Before a longer, harder one, the International Society of Sports Nutrition (ISSN) position stand on nutrient timing says it is commonly recommended to eat carbohydrate-rich snacks or meals for several hours before higher-intensity exercise of more than 90 minutes.¹ A review of carbohydrate for athletes adds that this is important for competition and for high-intensity training.² Before a shorter run, a meta-analysis found that eating first improved performance in prolonged aerobic exercise but not in shorter aerobic exercise.³

The position stand’s evidence comes from healthy, exercising adults, in particular highly trained ones, and the trials it describes in detail were in cyclists, not runners.¹ So what is good to eat before a run? The parts of these sources we could read give principles, not a menu, and don’t recommend or rank particular foods.

Below are the timings by kind of run, then the days before a race, then a table to apply it and what the research does not cover. Whatever you change, try it on a training run before you rely on it in a race.

Why food before a run matters at all

A joint position statement of the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada says the performance of, and recovery from, sport are enhanced by well-chosen nutrition strategies.⁴ It gives guidelines for the type, amount and timing of food and fluids, for athletes in general rather than recreational runners in particular.⁴ Each claim in this guide links to its source, and our editorial standards say how each one is checked.

The 2011 review says carbohydrate availability is increased by eating carbohydrate in the hours or days before a session.² It calls this important for competition, or for high-intensity training where you want to perform at your best.²

This guide is general information. For a nutrition plan made for you, the joint statement says athletes should be referred to a registered dietitian/nutritionist.⁴

How long before a run, and how much?

What and when to eat before a run depends on how long and how hard the run is, so the research is split the same way here.

Shorter runs

A 2018 meta-analysis pooled 46 studies comparing exercise after eating with exercise after fasting.³ Eating beforehand improved performance in prolonged aerobic exercise, but not in shorter-duration aerobic exercise.³ Its abstract does not say where shorter ends and prolonged begins, or who took part, so this guide does not put a time or distance on it. The authors say further research is needed on fasted and fed exercise, so this is not settled.³

That finding is about performance only. It does not show that running without eating is right for you: if you run better having eaten, eat.

Longer, harder runs

For a run that is both long and hard, the ISSN position stand says it is commonly recommended to eat snacks or meals high in carbohydrate for several hours before exercise of higher intensity (at least 70% of VO2max) and longer duration (more than 90 minutes).¹ A 2022 narrative review of carbohydrate for endurance athletes calls 1–4 g of carbohydrate per kg of body mass the general guideline for a pre-exercise meal, and expects further research to refine it.⁵

The evidence is mixed: the position stand notes that not all studies have shown a performance benefit from carbohydrate before exercise.¹

These are the days to think about food first, such as a hard long run (see how a marathon training plan is built). On a plan where most of your running is easy, and the hard days are sessions such as a tempo run, most days are not both long and hard.

The last hour or two

In the final hours before competition, the ISSN position stand says another priority is keeping a favourable balance with the digestive system and not eating or drinking too much.¹ It also says a certain degree of dogma still clouds the advice to eat particular types of carbohydrate in that time.¹

A 2022 review of endurance athletes says rebound hypoglycaemia, a drop in blood glucose, can occur in some athletes when they start exercise close to a meal.⁵ One study described in the position stand (its population isn’t given) found that taking carbohydrate closer to the start, 15 min rather than 75 min before, made those symptoms less likely.¹ A 1997 review of studies that gave carbohydrate at least 60 min before exercise, summarised in the same position stand, found no adverse effect on performance.¹

This evidence is thin and mixed: one study, a review from 1997 and a narrative review, and the effect is described in some athletes, not all. If eating shortly before running doesn’t suit you, try a different timing on a training run, not on race day.

The days before a race

The sources here talk about the days before a race, particularly one long enough to deplete muscle glycogen, the carbohydrate stored in your muscles: the ISSN position stand encourages athletes to consider carbohydrate loading in the days before such an event.¹ A 2026 meta-analysis of 63 trials with 641 recreationally active and endurance-trained participants found that muscle glycogen depends mainly on how much carbohydrate is eaten, with the length of the higher intake, training status and exercise also playing a part.⁶ It concluded that to raise pre-competition muscle glycogen significantly, athletes should eat more than 8 g of carbohydrate per kg of body mass per day for 36–48 h before competition.⁶ It measured glycogen in the muscle, not race times, and the authors say heterogeneity and confounding in earlier research make these recommendations uncertain.⁶ This guide is not a loading plan; for the week before a race, see how long a marathon taper should be.

How to apply it

What the sources support for each kind of run, and where it comes from
Run	What the sources support	Source
Short run	Eating first did not improve performance in shorter aerobic exercise, though it did in prolonged exercise	Aird 2018, meta-analysis of 46 studies³
Long, hard run or race	Carbohydrate-rich snacks or meals for several hours before higher-intensity exercise of more than 90 minutes are commonly recommended; a review calls 1–4 g per kg of body mass the general guideline, to be refined; not all studies found a benefit	Kerksick 2017, ISSN position stand; Podlogar 2022, review^{1, 5}
Final hour or two	Keep a favourable balance with the digestive system and don’t eat or drink too much; some athletes get rebound hypoglycaemia starting close to a meal, and one study found intake closer to the start made those symptoms less likely	Kerksick 2017, ISSN position stand; Podlogar 2022, review^{1, 5}
Days before a race (especially a long one)	Carbohydrate loading before competition that will deplete muscle glycogen; more than 8 g per kg of body mass per day for 36–48 h before competition to raise glycogen, with uncertainty	Kerksick 2017, ISSN position stand; Jones 2026, meta-analysis^{1, 6}

Practise on a training run, ideally one like the run or race you are preparing for. Change one thing at a time, the timing or the amount, so you can tell what made the difference. On race day, eat what you have already tried in training.

In RunFast

RunFast’s plans label each session, and Today shows the day’s session with its target pace. A plan has one long run a week and keeps about 80% of running easy, with 0–2 quality sessions a week, tempo or threshold runs and intervals, depending on the phase and your level. Paces come from Daniels’ VDOT model, from a recent race or your fitness level. So the plan shows which kind of day it is, and you can match it to a row of the table above.

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What the research does not cover

If you searched for what not to eat before a run, these sources don’t give a list. The parts we could read don’t name or rank foods, and give no rule on fat, fibre or protein before a run. They don’t say how much food a particular runner can tolerate before running, and the 2018 meta-analysis doesn’t define a shorter run. We found little on women or on beginners.

The ISSN position stand’s evidence is in healthy, exercising adults, in particular highly trained ones.¹ Not all studies have shown a performance benefit from carbohydrate before exercise.¹ The authors of the 2018 meta-analysis say more research is needed on fasted and fed exercise.³ The 1–4 g per kg guideline is expected to be refined.⁵ The 2026 meta-analysis calls its own loading recommendation uncertain.⁶

In practice, treat the timings and amounts here as starting points to test, not rules.

Common questions

What should I eat before a morning run?

If the run is short, the 2018 meta-analysis found no performance benefit from eating first in shorter aerobic exercise.³ If it is both hard and longer than 90 minutes, the commonly recommended approach is a carbohydrate-rich snack or meal for several hours before.¹ An early start leaves less time to digest, and one study in the ISSN position stand (its population isn’t given) found that carbohydrate closer to the start, 15 min rather than 75 min before, made symptoms of rebound hypoglycaemia less likely.¹ Try your morning routine before a training run first.

What should I eat the night before a long run?

The sources talk about the days before an event rather than one evening meal: the ISSN position stand encourages athletes to consider carbohydrate loading in the days before an event that will significantly deplete muscle glycogen.¹ The 2026 meta-analysis’s figure is more than 8 g of carbohydrate per kg of body mass per day for 36–48 h before competition, and its authors call the recommendation uncertain.⁶ None of the parts we could read sets a rule for the night before a training run.

What should I eat before a 5K or 10K?

None of the parts of these sources we could read is specific to either distance. The same split applies: no performance benefit from eating before shorter aerobic exercise in the 2018 meta-analysis, and carbohydrate-rich snacks or meals in the hours before commonly recommended for higher-intensity exercise of more than 90 minutes.^{3, 1} Where your race falls depends on how long it takes you and how hard you run it; the 2018 meta-analysis’s abstract doesn’t define “shorter”.

Can I eat right before a run?

Some athletes get rebound hypoglycaemia when they start exercise close to a meal.⁵ One study (its population isn’t given) found that taking carbohydrate 15 min rather than 75 min before the start made those symptoms less likely, and a 1997 review of studies giving carbohydrate at least 60 min before exercise found no adverse effect on performance.¹ The evidence is thin, so if you want to eat an hour before a run or closer, try it in training first and don’t eat or drink too much.

This guide is general information, not medical advice. If you have an injury, a health condition or are pregnant, ask a doctor or physiotherapist before changing how you train or eat.

Sources

Kerksick CM, Arent S, Schoenfeld BJ, Stout JR, Campbell B, Wilborn CD, Taylor L, Kalman D, Smith-Ryan AE, Kreider RB, Willoughby D, Arciero PJ, VanDusseldorp TA, Ormsbee MJ, Wildman R, Greenwood M, Ziegenfuss TN, Aragon AA, Antonio J. International society of sports nutrition position stand: nutrient timing. Journal of the International Society of Sports Nutrition. 2017. doi:10.1186/s12970-017-0189-4
Burke LM, Hawley JA, Wong SH, Jeukendrup AE. Carbohydrates for training and competition. Journal of Sports Sciences. 2011. doi:10.1080/02640414.2011.585473
Aird TP, Davies RW, Carson BP. Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis. Scandinavian Journal of Medicine & Science in Sports. 2018. doi:10.1111/sms.13054
Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Medicine and Science in Sports and Exercise. 2016. doi:10.1249/mss.0000000000000852
Podlogar T, Wallis GA. New Horizons in Carbohydrate Research and Application for Endurance Athletes. Sports Medicine. 2022. doi:10.1007/s40279-022-01757-1
Jones RO, Areta JL, Fortis HO, Pugh J, Louis JB. Dietary Carbohydrate Intake and Skeletal Muscle Glycogen: A Systematic Review and Meta-Analysis to Determine Optimal Carbohydrate Loading Strategies. Scandinavian Journal of Medicine & Science in Sports. 2026. doi:10.1111/sms.70379