Should you eat before running? Decide by the run
| Type of run | Eat first? | Why |
|---|---|---|
| Easy, under an hour | Your choice | BHF: fine to skip for low-intensity or under-an-hour sessions |
| Hard session (intervals, tempo) | Yes, something light | BDA: harder training needs more carbohydrate |
| Long run, over an hour | Yes | BHF: eat beforehand for over an hour; Aird 2018: eating helped longer efforts |
| Race day | Yes, a breakfast you've practised | Don't try anything new on the day |
If you do eat, the timings are simple: a meal 2 to 3 hours before, or a light carb snack 1 to 2 hours before. The foods themselves are in what to eat before a run.
What the research says about running fasted
In 2018, Aird, Davies and Carson pooled 46 studies comparing fasted and fed exercise. Eating beforehand improved performance in prolonged aerobic exercise but not in shorter aerobic exercise. Fasted exercise did raise the amount of fat circulating in the blood after the session.
That last finding gets turned into “fasted running burns more fat”. That isn't what the review measured, and it doesn't show you'll lose more body fat. The authors say more research is needed. So if you like running before breakfast, carry on. If you don't, there's no reason to force it.
If you run without eating, eat afterwards
The BHF says that if you haven't eaten for a few hours before exercising, it's important to have a balanced meal soon after, within an hour. See what to eat after a run.
When you should eat before running next time
If you feel flat or light-headed, or you can't finish the session, eat something beforehand next time. If you feel dizzy or unwell, stop. The NHS Couch to 5K advice is to listen to your body and stop if something doesn't feel right. Dizziness that keeps happening is one for your GP. If you're diabetic or take medication, check with your GP or a registered dietitian before running fasted.
FAQs
Is it better to run on an empty stomach?
Not for performance on longer runs: a 2018 meta-analysis found that eating beforehand improved prolonged aerobic performance. For short, easy runs, it made no clear difference, so it's your choice.
Does running fasted burn more fat?
Fasted exercise raised the fat circulating in the blood after the session in the 2018 review, but that isn't the same as losing more body fat, and the review didn't show that.
Can I run straight after eating?
It's about comfort. A meal is easier 2 to 3 hours before a run, and a light snack 1 to 2 hours before (BHF, NHS).
How long can I run without eating?
The BHF says you can skip eating before low-intensity sessions or ones under an hour. For anything longer, eat beforehand.
Sources
- 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. Scand J Med Sci Sports 2018;28(5):1476-1493. pubmed.ncbi.nlm.nih.gov/29315892
- British Heart Foundation, Food for fitness: what should I eat before a workout? (opened 1 Nov 2026). www.bhf.org.uk/informationsupport/heart-matters-magazine/nutrition/food-for-fitness
- British Dietetic Association, Sport and exercise food fact sheet (opened 1 Nov 2026). www.bda.uk.com/resource/sport-exercise-nutrition.html
- NHS Better Health, Couch to 5K running plan (opened 1 Nov 2026). www.nhs.uk/better-health/get-active/get-running-with-couch-to-5k/couch-to-5k-running-plan