Healthy eating for marathon training: how to eat through a build

Healthy eating for marathon training is less about clean food and more about enough food. Eat enough total energy, scale your carbohydrate to how hard the day is, spread protein across the day, and keep the rest of your plate normal: fruit, vegetables, some fat, foods you actually like. The most common nutrition mistake in a marathon build isn't the wrong snack. It's quietly under-eating for 16 weeks and wondering why the long runs feel awful.

Below: daily carb targets by training day, protein, the case against dieting mid-build, what a few typical days look like, and where the fueling-specific stuff lives. The week itself, which day is hard and which is easy, is the job of a coach that programs your week for you. What goes on the plate is this post.

One note up front: this is general practice, not a personal prescription. If you have diabetes, a GI condition, a history of disordered eating, or any other clinical issue, see a doctor or a registered dietitian. A registered dietitian who works with endurance athletes is also the right call if you want actual numbers built around you.

Healthy eating for marathon training: the principles

1. ›Eat enough. Marathon training burns a lot. If you're always hungry, always tired, or your easy runs feel hard, look at your plate before your plan.
2. ›Carbs follow the training. More on big days, less on rest days.
3. ›Protein at every meal. Not a giant shake once a day. Moderate amounts, spread out.
4. ›Fuel the long run. Before, during and after. It's the session that most rewards eating well.
5. ›Boring is fine. The best training diet is one you can repeat for four months.

Those principles don't change much by distance. If you're building toward a shorter race first, a half marathon training plan has the same shape with smaller numbers, and the eating scales down with it.

The single most important session to eat around is the long run. A guide to what to eat before a long run covers the pre-run meal, the night before and fueling during. This post is about the other six days.

How many carbs do marathon runners need?

The joint position stand from the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada gives daily carbohydrate targets by training load (Thomas, Erdman and Burke, 2016):

Most marathon runners sit in the moderate-to-high rows, depending on the week. The same table notes these targets matter most when the session needs to be high quality or high intensity, and that when quality matters less, carbohydrate can be chosen to suit energy goals, food preferences and convenience. In plain terms: fuel your hard days and long runs properly, and don't stress about the exact gram count on a rest day.

Here's what that looks like for a 70 kg runner. It's just multiplication, so do it for your own number:

You don't need to weigh your rice. The point is the pattern: noticeably more on the long-run day and the day before it than on a Tuesday off. Bigger portions of pasta, rice, potatoes, bread, oats, fruit and juice on big days; normal portions otherwise.

Protein: spread it out

The position stand puts daily protein for athletes at roughly 1.2 to 2.0 g/kg, and recommends getting it as moderate amounts across the day: about 0.3 g/kg after key sessions and every 3 to 5 hours over multiple meals (Thomas, Erdman and Burke, 2016). It also notes that eating enough energy, particularly from carbohydrate, matters so that protein goes toward building and repair instead of being burned as fuel.

For a 70 kg runner, that's roughly 84 to 140 g a day, in portions of around 20 g. Four meals and snacks with a decent protein source each, and you're there. Meat, fish, eggs, dairy, tofu, tempeh, beans and lentils all count.

If you also lift, the same protein covers both jobs. The good news: you don't need to time it to the minute. A meta-analysis by Schoenfeld, Aragon and Krieger (2013) found that total protein intake was the strongest predictor of muscle growth, and that adequate protein combined with resistance training is the key factor, not precise timing around the session.

Fat, fruit, vegetables and the rest

Fat isn't the enemy. The position stand says most athletes eat 20% to 35% of their energy from fat, and discourages going below 20% for long stretches because it narrows the variety of food you eat (Thomas, Erdman and Burke, 2016). Olive oil, nuts, avocado, fish and dairy are all welcome.

Fruit and vegetables are where most of your vitamins and minerals come from. The position stand says supplements are generally unnecessary for athletes eating a varied diet with enough energy. The exceptions are deficiencies, and two matter for runners:

• ›Iron. The position stand names distance runners among the athletes at greatest risk of poor iron status, and says they should be screened regularly. Low iron needs a blood test and a doctor, not a guess and a supplement.
• ›Vitamin D and calcium. Both matter for bone health. If you train mostly indoors or live somewhere dark, ask your doctor whether it's worth testing.

High-fiber food is great most of the time. The exception is the meal before a long run, a race or a hard session, when lower-fiber choices sit better.

Don't diet during a marathon build

This is the big one. A marathon build is a bad time to cut calories hard.

The position stand describes low energy availability, where you eat too little to cover both your training and your body's normal functions, and links it to a long list of problems under the name Relative Energy Deficiency in Sport (RED-S). Potential performance effects it lists include decreased endurance, increased injury risk, decreased training response and decreased muscle strength (Thomas, Erdman and Burke, 2016). It also notes low energy availability can happen by accident during high-volume training, without anyone trying to diet.

Signs worth taking seriously: constant fatigue, easy runs that feel hard, getting sick a lot, missed or irregular periods, or injuries that keep coming back. Any of those is a reason to see a doctor or a registered dietitian. Not a reason to train harder.

If body composition is a goal, it can wait for the off-season. Run the marathon fed.

What a few days actually look like

No meal plan. Just the shape, using foods most people already eat.

Rest day. Normal meals. Protein at each. Plenty of vegetables, a normal serving of carbs. This is the day for the big salad and the lentil soup.

Easy run plus lift. Breakfast with carbs and protein, a snack before the run if it's after work, a proper dinner with carbs and protein after the lift. Nothing fancy.

Day before the long run. Carbs bumped up at every meal, dinner carb-forward and familiar, fiber and fat eased back a little in the evening.

Long run day. A carb breakfast you've tested, carbs during the run once it passes an hour, then a proper meal with carbs and protein afterward. Then snack through the afternoon. You've earned it and you'll need it.

Fueling the long runs and the race

Tune-up races are the dress rehearsal. If a half is on your calendar mid-build, use it to practice the whole routine, including the part people forget: what to eat after a half marathon is mostly a normal meal with carbs and protein, reasonably soon, so the following week of marathon training doesn't start on empty. Then work backward through what to eat the night before a half marathon, race breakfast, and fuel at your planned timing.

Your everyday eating fills the tank. Your long runs are where you learn to top it up on the move. The position stand targets 30 to 60 g of carbohydrate per hour for efforts of 1 to 2.5 hours and up to 90 g per hour beyond about 2.5 to 3 hours (Thomas, Erdman and Burke, 2016). How to build up to that without your stomach filing a complaint is covered in our energy gels for marathon training guide.

Eating after everyday runs

Most of your runs aren't long runs. After a 40-minute easy run, you don't need a recovery protocol. You need your next meal. If your next session is less than eight hours away, though, the position stand's fast-refuel guideline of 1 to 1.2 g/kg of carbohydrate per hour for the first four hours applies (Thomas, Erdman and Burke, 2016). That's mostly relevant for double days and run-then-lift days. For shorter efforts, a guide to what to eat after 5k runs and other everyday sessions has the short version.

Hydration and alcohol

Drink to thirst through the day, and more on hot days and long-run days. Pale yellow urine is a reasonable rough guide.

Alcohol isn't banned. The position stand does say it may interfere with recovery after exercise by impairing glycogen storage, rehydration and muscle protein synthesis, and encourages athletes to minimize or avoid it in the post-exercise period when recovery is a priority (Thomas, Erdman and Burke, 2016). Friday drinks before a Saturday long run is a choice you'll feel at mile 12.

Common mistakes

• ›Eating like a rest day every day. Marathon training is not a rest day.
• ›Cutting carbs to lose weight mid-build. Then wondering why the long runs collapse.
• ›One giant protein shake instead of protein at meals. Spread it out.
• ›Copying an elite's meal plan. They run twice your mileage. Eat for your training, not theirs.

How exrsz handles marathon training

exrsz builds a periodized plan from your goal, your schedule, your level and your equipment, with running and lifting balanced in one plan. It adapts each week to how you actually trained and reshuffles missed sessions, so you always know which days are big and which aren't. The groceries are still on you.

FAQ

What is a healthy diet for marathon training?

Enough total food, carbohydrate that rises and falls with your training load, moderate protein at every meal, and plenty of fruit, vegetables and some fat. The joint ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada position stand gives 5 to 7 g/kg of carbs a day for about an hour of training, and 6 to 10 g/kg for 1 to 3 hours (Thomas, Erdman and Burke, 2016).

How much protein do marathon runners need?

The position stand puts athletes' daily protein at around 1.2 to 2.0 g/kg, spread as roughly 0.3 g/kg after key sessions and every 3 to 5 hours (Thomas, Erdman and Burke, 2016). For most runners that's a normal protein source at every meal.

Can I lose weight while training for a marathon?

A marathon build is a poor time to diet. The position stand links low energy availability to decreased endurance, increased injury risk and a weaker training response (Thomas, Erdman and Burke, 2016). If body composition is a goal, talk to a registered dietitian and plan it for the off-season.

Do marathon runners need supplements?

Usually not, if you eat a varied diet with enough energy. Iron and vitamin D are the common exceptions, and the position stand says distance runners should be screened for iron status regularly (Thomas, Erdman and Burke, 2016). Get tested before you supplement.