The week before a marathon is when your nutrition shifts from fueling training to stockpiling energy. Your primary goal is to maximize glycogen, the stored carbohydrate in your muscles and liver that serves as your main fuel source over 26.2 miles. The strategy is straightforward: eat more carbohydrates, ease up on fiber and fat, and avoid anything that might cause stomach trouble on race day.
Carb Loading: How Much and When
Carb loading isn’t just eating a big pasta dinner the night before. Done properly, it’s a deliberate increase in carbohydrate intake over the final 36 to 48 hours before the race, targeting 10 to 12 grams of carbohydrates per kilogram of body weight during that window. For a 70 kg (154 lb) runner, that’s 700 to 840 grams of carbs spread across roughly two days. That’s a lot of food, and it’s why runners start adjusting their plates earlier in the week.
During the first half of race week (Monday through Wednesday for a Sunday race), you don’t need to hit those extreme numbers. Instead, aim for a moderately high carb intake, around 5 to 7 grams per kilogram, while keeping meals balanced. Think of this as a ramp-up phase. You’re eating a bit more rice, bread, pasta, and potatoes than usual, but not stuffing yourself.
Starting Thursday or Friday, shift more aggressively toward carbohydrates. This is when white rice, plain bagels, pancakes, pretzels, fruit juice, and low-fiber cereals become your best friends. The carbs you eat now get converted into glycogen and stored in your muscles, giving you the fuel reserve that prevents you from hitting the wall around mile 20. Your muscles can store roughly 2,000 calories of glycogen when fully loaded, compared to about 1,500 when you eat normally.
What to Actually Put on Your Plate
Good carb-loading foods are energy-dense but easy on your stomach. White rice, white pasta, white bread, bagels, oatmeal (if you tolerate it), potatoes without the skin, bananas, applesauce, pancakes, and honey all work well. Sports drinks and fruit juice count toward your carb totals too, and they’re useful if you’re struggling to eat enough solid food.
You still need protein during race week to support muscle recovery from your final training sessions. A reasonable target is 1.6 to 2.2 grams of protein per kilogram of body weight per day. Chicken breast, eggs, Greek yogurt, and fish are all solid choices that pair easily with carb-heavy meals. Just don’t let protein crowd out the carbohydrates on your plate, especially in those final two days.
Fat doesn’t need to be eliminated, but it should take a back seat. High-fat foods slow digestion, which is fine on a normal day but counterproductive when you’re trying to pack in carbs. Limit fried foods, heavy cream sauces, rich desserts, and anything cooked in a lot of butter or oil. A little fat in your meals is fine. A bacon cheeseburger the night before is not.
Managing Fiber and Digestion
Gastrointestinal distress is one of the most common reasons runners underperform on race day, and fiber is often the culprit. Starting a few days out, begin reducing high-fiber foods, especially if you know your stomach is sensitive. That means cutting back on raw vegetables, beans, broccoli, Brussels sprouts, cabbage, cauliflower, kale, and whole grains that are extremely high in fiber.
This doesn’t mean you can’t eat any fruits or vegetables. Bananas are a reliable option all week. Cooked vegetables are easier to digest than raw ones, and peeled fruit or fruit juice gives you the carbs and micronutrients without the roughage. If you normally eat a salad with every meal, race week is the time to swap it for a side of white rice.
Everyone’s gut is different. Some runners eat a large, fiber-rich dinner the night before a race with no issues. Others need two or three days of a low-residue diet to feel comfortable at the starting line. You should know from your long training runs what your stomach can handle. Race week is not the time to experiment.
A Sample Day-by-Day Approach
Monday Through Wednesday
Eat balanced meals with a carb emphasis. You’re still eating vegetables, some healthy fats, and your normal protein sources, just tilting each meal a little more toward starches. A typical dinner might be grilled chicken with a large serving of rice and some cooked carrots. Snack on pretzels, crackers, or fruit between meals. Stay well hydrated but don’t overdo water to the point you feel bloated.
Thursday and Friday
This is when the real carb loading begins. Increase portion sizes of starches at every meal. Breakfast could be a large stack of pancakes with maple syrup and a banana. Lunch might be two bagels with a thin layer of peanut butter and honey. Dinner could be a big plate of pasta with a simple tomato sauce and some plain chicken. Sip on sports drinks between meals if you need extra carbs. Start dialing back fiber, especially at dinner.
Saturday (Race Eve)
Eat your largest carb meal at lunch rather than dinner. This gives your body more time to digest and store glycogen. Keep dinner moderate in size, familiar, and low in fiber and fat. A classic choice is plain pasta with marinara sauce, or rice with grilled chicken and a banana for dessert. Eat early enough that you’re not going to bed with a full stomach. Avoid anything spicy, heavily seasoned, or new to you.
Foods to Avoid All Week
Some foods carry a higher risk of causing GI distress during the race, and they’re worth avoiding for most of the week, not just the night before:
- High-fat and fried foods: burgers, fries, creamy sauces, rich desserts
- Gas-producing vegetables: broccoli, beans, cabbage, cauliflower, Brussels sprouts
- Carbonated beverages: soda, sparkling water, beer
- Alcohol: it impairs glycogen storage and disrupts sleep
- Spicy foods: anything that could irritate your stomach
- Unfamiliar foods: a new restaurant or exotic cuisine is a gamble you don’t need
The underlying principle is simple: nothing new, nothing risky. Every meal this week should be something your body has handled easily before.
Race Morning Breakfast
Your final pre-race meal should happen about 2 to 3 hours before the starting gun. The goal is 1 to 4 grams of carbohydrates per kilogram of body weight, depending on your tolerance. For most runners, that looks like a bagel with honey, a banana, and some sports drink, or a bowl of oatmeal with fruit.
Keep it low in fat, low in fiber, and low in protein. This meal isn’t about fueling the whole race. It’s about topping off your liver glycogen, which gets partially depleted overnight while you sleep. Eat foods you’ve practiced with before your long runs. If you’ve never eaten a peanut butter and jelly sandwich at 5 a.m. before a 20-miler, don’t try it on race morning.
Hydration Throughout the Week
Hydration matters just as much as food during race week. Drink consistently throughout the day rather than chugging large amounts at once. Water is your primary fluid, but sports drinks serve double duty by adding electrolytes and extra carbohydrates. Your urine should be pale yellow. If it’s clear, you may be overhydrating, which can dilute sodium levels.
Avoid alcohol entirely in the final two to three days. It acts as a diuretic, interferes with glycogen storage, and disrupts sleep quality. Even a single glass of wine the night before can affect how you feel at mile 10. Save the celebration for after you cross the finish line.