Half marathon nutrition plan: what to eat race week

Photo by Stephen Leonardi on Pexels

You’ve done the long runs. You’ve survived the hill sessions, the 6am alarms, the week you had to swap your Tuesday tempo for Thursday because your kid had a school play. The training is basically banked. What happens in your kitchen over the next seven days can still make or break that finish time — and most runners get it wrong in one of two directions: they panic-eat pasta like it’s their job, or they ignore food entirely and just hope their legs show up.

Neither works. A half marathon nutrition plan the week before race day isn’t about dramatic changes — it’s about small, deliberate adjustments that top up your glycogen stores, keep your gut calm, and stop you from lining up on Sunday feeling either bloated or empty. This isn’t marathon-level carb loading. You don’t need three days of pasta and existential dread. You need a plan that fits around your actual week — work meetings, the school run, the fact that you still have to cook dinner for other people.

Here’s what that week actually looks like, day by day, with no mystery supplements or “detox” nonsense.

Why race week nutrition matters more than people think

A half marathon burns through roughly 800–1,200 calories depending on your pace and size, and a good chunk of that comes from stored carbohydrate (glycogen) in your muscles and liver. Most recreational runners store enough glycogen for 90–120 minutes of running at moderate effort — which is exactly why some people feel fine at 10K and start fading at mile 10. You’re not necessarily undertrained. You might just be under-fuelled going into the start line.

The goal of this week isn’t to “carb load” in the dramatic marathon sense — that’s really a 26.2-mile problem, and we’ve covered it properly in our guide to carbohydrate loading before a marathon. For a half marathon, you’re doing something gentler: topping up glycogen stores that are already decent, settling your gut, and avoiding anything that introduces risk this late in the game.

The week-before breakdown: what to actually eat

Think of the week in three phases, not seven identical days.

Monday to Wednesday — normal eating, dialled in slightly

This is not carb-loading territory. Eat your usual balanced meals: protein, vegetables, whole grains, healthy fats. If anything, this is the window to make sure you’re getting enough iron and B vitamins — tired legs during taper week are sometimes just low energy availability from a few too many skipped lunches during peak training.

Thursday to Saturday — gentle carb increase, fibre decrease

This is where the real adjustment happens. Shift your plate ratio so carbohydrates make up a bigger share — roughly 55–65% of your calories — while gradually dialling back high-fibre foods (raw vegetables, beans, wholegrain everything) that are brilliant for your gut on a normal Tuesday but risky 48 hours before you need your bowels to behave mid-run.

Race day minus 1 — familiar, boring, carb-forward

Nothing new. Nothing “healthy” you’ve never tried. This is not the day to discover quinoa.

The taper doesn’t mean you eat less

This is the trap a lot of runners fall into. Training volume drops during taper week, so instinct says cut calories too. Don’t. Your body is still repairing muscle, topping up glycogen, and preparing for race effort — it needs the fuel even though you’re running less. Eating less this week is one of the most common reasons runners feel flat and heavy-legged on race morning despite “resting.”

If you’re someone who’s running partly to manage weight, this is genuinely not the week to create a calorie deficit — our piece on whether running helps you lose weight goes into why race week specifically isn’t the time to chase that goal. Eat to the appetite your training has built, not to some imagined “I’m tapering so I need less” logic.

Hydration: start Thursday, not Saturday night

Chugging two litres of water the night before a race doesn’t hydrate you — it mostly just gets you up three times in the night to pee. Proper hydration is a cumulative thing across several days, not a last-minute fix.

From Thursday onward:

• Aim for pale yellow urine, not clear (clear usually means overhydrated and flushing electrolytes)
• Add an electrolyte drink on Friday and Saturday, especially if you’re a heavy sweater or racing somewhere warm
• Don’t suddenly introduce a new electrolyte brand on race morning — test it during an easy run this week first

If you want a proper breakdown of options, our comparison of electrolyte drinks for runners is worth a read before you commit to one for Sunday.

The gut problem nobody warns you about

Half marathon GI distress is almost always a race-week mistake, not a race-day one. The usual suspects:

• A huge bowl of chilli or curry on Thursday “because carbs”
• Trying a new energy gel flavour for the first time mid-race
• Too much caffeine on an empty stomach race morning
• Alcohol on Friday night that dehydrates you by Saturday

If your stomach has ever let you down mid-run, this is the week to be boring on purpose. Our guide to gut health for runners has more detail, but the short version: reduce fibre, avoid very spicy or very fatty food from Thursday, and never test anything new within 72 hours of the start line.

Race morning: what and when

For a half marathon starting mid-morning (common in the UK), this timeline works for most people:

If your half marathon finish time is under 90 minutes, you may not need mid-race fuelling at all beyond maybe one gel. If you’re running 2 hours 15 or longer, plan on 2–3 gels and make sure you’ve practised taking them on a long run, not for the first time on race day. Our best energy gels guide covers which ones are gentlest on sensitive stomachs.

What to actually avoid this week

• Alcohol — even one or two drinks Friday night affects sleep quality and hydration into Saturday
• New foods or restaurants — save the exciting dinner for after the race
• Excess fibre on Thursday–Saturday — this means going easy on beans, lentils, raw broccoli, bran cereal
• Skipping meals to “feel light” — this backfires as low energy at mile 8, not mile 1
• Over-hydrating the night before — spread it across the week instead

The Honest Takeaway

• Start your carb and hydration adjustments on Thursday, not Saturday night — this week is about gradual topping up, not a last-minute scramble.
• Keep taper week calories normal or even slightly higher — reduced training volume doesn’t mean reduced fuel needs.
• Lower your fibre intake from Thursday onward to protect your gut, and never trial a new gel, drink, or breakfast for the first time on race morning.
• Eat a carb-forward, low-fibre dinner on Saturday that you’ve eaten before — boring and familiar beats “healthy and new” this week.
• Race morning: eat 2–3 hours before the gun, keep it simple, and only use caffeine or gels you’ve already tested on a training run.

Next read: Pack it all with our half marathon race day checklist