Nutrition — The Marathon

Disclaimer. Individual responses to fueling vary widely. Practise everything in training before race day. If you have specific dietary needs or medical conditions, work with a registered sports dietitian.

Daily fueling in training

The marathon runs on carbohydrate. Your daily diet through a training block should be built around enough of it to fuel sessions and recover from them. Rough guidance:

Carbohydrate: 5–8 g per kg of body weight per day during heavy weeks; lower on rest days, higher around hard sessions.
Protein: 1.4–1.8 g per kg per day, spread across meals. Critical for adapting to training.
Fat: the rest. Don't fear it; just don't replace carbs with it.
Iron, vitamin D, calcium: watch these — endurance runners are over-represented in deficiencies. Bloodwork annually if you're training seriously.

Eat real food most of the time. Sports nutrition is for sport — gels and drinks earn their place around hard sessions, not at lunch.

Fueling long runs

Long runs are dress rehearsals. Use them to train your gut: fuel earlier and more often than feels necessary, so race-day intake feels routine.

Anything under 75 minutes: probably nothing needed beyond water.
75–120 minutes: 30–60 g of carbs per hour.
120 minutes plus: 60–90+ g per hour, ideally a glucose+fructose mix to maximize absorption.

Start fueling within the first 30 minutes — don't wait until you feel low. The gut takes time to absorb; if you're already running on empty, gels won't catch you up.

Race week

Three to four days out: carb-load

For 2–3 days before the race, raise carbohydrate to 8–12 g per kg per day. This isn't "eating more pasta at dinner" — it's actively replacing fat and some protein in your meals with carbs (rice, potatoes, bread, fruit, oats, sports drinks). Done well, you'll gain 1–2 kg of stored glycogen and water; that's the goal.

Day before

Continue eating carbs through the day. Your last big meal should be lunch or early evening — not late. Avoid anything new, anything especially high in fat or fiber, and anything that might disagree with you. Hydrate steadily; don't binge water at bedtime.

Race morning

Wake 3–4 hours before the gun.
Eat a familiar carb-heavy breakfast — 1–4 g of carbs per kg: oatmeal, toast and jam, a bagel, banana, sports drink. Practice this in training.
Sip ~500 ml of fluid in the 2 hours pre-race; stop drinking heavily 30 minutes out.
Caffeine, if you use it, ~60 minutes before — at a dose you've practiced.

During the race

The current best practice for trained runners is 60–90 g of carbohydrate per hour, with elite athletes pushing 100–120 g/hr. For most amateurs, hitting 60 g/hr is plenty — and a step up from "a gel every 45 minutes" intake of a few years ago.

Practical patterns:

A gel (typically ~22–25 g of carbs) every 25–30 minutes, starting at 30–40 minutes in.
Combine with sports drink at aid stations to add carbs and electrolytes.
Use a glucose + fructose blend (e.g. 2:1) — your gut absorbs them through different transporters and can take in more total fuel.
Caffeinated gels in the second half can help, especially in the final hour.

The wall. Hitting "the wall" at ~30 km is glycogen depletion: the muscle fuel runs low and your pace collapses. The fix is mostly preventative — fuel before you need to.

Hydration

Drink to thirst. The era of "drink as much as possible" is over — overdrinking causes hyponatremia, which is far more dangerous than mild dehydration. For most runners on a cool day, 400–800 ml per hour is plenty.

In hot conditions, increase intake and add electrolytes (sodium especially).
Heavy/salty sweaters: pre-race weigh-in/weigh-out during long training runs to estimate sweat rate.
Sports drinks pull double duty: water + carbs + electrolytes.

Next: Recovery — what happens after the gel runs out.