Half Marathon Nutrition: The Complete Guide to What to Eat and When

Half marathon nutrition isn't one topic, it's several different problems that get lumped under the same heading: what you eat on an ordinary training day, how your diet should shift as your mileage builds, how to fuel your weekly long run, and what to eat in the day or two before and during the race itself. This page covers the big-picture principles that apply across all of them, then points you to the specific guide for whichever problem you're actually trying to solve.

The Big Picture: Carbs, Protein, Fat, and Water

These ranges apply broadly across a training block, but they're not the whole story. How much you actually need shifts with your weekly mileage, and what you eat in the hours before or during a specific run is a different question from your daily baseline. That split is what this site's nutrition guides are built around.

A Note on Caffeine

A moderate dose of caffeine before a run, roughly what's in a cup of coffee, can improve alertness and reduce your perceived effort, which is why many runners use it on race morning. Test it in training first, though. If you notice stomach issues or jitteriness, a standard non-caffeinated energy gel is a safer bet on race day than experimenting with a new caffeine source.

Which Guide Do You Actually Need?

If you only take one thing from this page, take this: don't try to solve your race-day fueling plan and your day-to-day training diet with the same set of rules. Use the table above to find the guide that matches what you're actually trying to figure out, and use a hydration calculator to turn the general water guidance into a number specific to you.

Frequently Asked Questions

What's the difference between everyday training nutrition and race-day fueling?

Everyday training nutrition is about consistently hitting your daily carbohydrate, protein, and fat targets to support recovery and adaptation across weeks of training. Race-day fueling is a narrower, more specific plan covering what and when to eat and drink in the day or two before the race and during the 13.1 miles themselves, and it's covered in its own dedicated guides.

How many carbs should a half marathon runner eat per day?

Aim for roughly 55 to 65% of your daily calories from carbohydrate during training, leaning toward the higher end during your heaviest mileage weeks. This is meaningfully more than a sedentary adult needs, since carbohydrate is what your muscles store as glycogen and burn during your runs.

How much protein does a half marathon runner need?

Most runners need about 1.2 to 1.4 grams of protein per kilogram of body weight per day, spread across three or four meals rather than concentrated in one. Protein repairs the muscle tissue that distance training breaks down, so it matters throughout your training block, not just after a hard run.

Is caffeine helpful for half marathon running?

A moderate dose of caffeine can improve alertness, sharpen focus, and reduce your perceived effort, which is why it's popular on race morning. It works well for most runners, but test it during training first. If it causes stomach issues, a standard non-caffeinated energy gel is a more reliable choice on race day.