The day before a run, your main goal is to top off your body’s stored energy by eating more carbohydrates than usual while cutting back on fiber, fat, and anything that might upset your stomach. For a long run or race, aim for 10 to 12 grams of carbohydrate per kilogram of body weight spread across the full day. For a 70-kilogram (154-pound) runner, that works out to roughly 700 to 840 grams of carbs, which is significantly more than a typical day’s intake.
Why Carbohydrates Matter More Than Anything Else
Your muscles store carbohydrate as glycogen, and glycogen is the fuel your body burns most efficiently during sustained effort. Those stores are limited. Topping them off the day before a long run gives you a larger energy reserve and delays the point where you hit the wall. The process works best when you start 36 to 48 hours before your run and pair it with rest or very light activity.
In practical terms, this means adding extra servings of carbohydrate-rich foods at every meal and snack while trimming your usual portions of protein and fat. You don’t need to eat drastically different foods. You just need to shift the ratio. If your normal dinner plate is one-third pasta and one-third chicken, flip it: two-thirds pasta, a smaller portion of chicken, and less oil or butter in the sauce.
The Best Foods To Load Up On
Stick with simple, easily digested carbohydrate sources. White rice, regular pasta, plain bagels, white bread, pancakes, tortillas, and potatoes (baked or roasted) are all reliable choices. These foods are calorie-dense, easy on the stomach, and low in fiber. Bananas, cooked vegetables, yogurt, juice, and sports drinks can fill in the gaps between meals.
A smart approach is to eat your largest meal at lunch rather than dinner. This gives your body more time to digest before you sleep and before the run itself. Follow that big lunch with a lighter carb-rich dinner, like a bowl of white rice with a small portion of chicken, and then a carbohydrate snack before bed, such as toast with jam or a banana.
Here’s what a full day might look like for someone preparing for a long race:
- Breakfast: Pancakes with syrup, a banana, and a glass of juice
- Mid-morning snack: A bagel with a thin spread of peanut butter
- Lunch (your big meal): A large plate of pasta with a light tomato sauce, white bread on the side, and a sports drink
- Afternoon snack: A granola bar and another piece of fruit
- Dinner: White rice with a small portion of grilled chicken and cooked zucchini
- Evening snack: Toast with jam or a bowl of low-fiber cereal
What To Cut Back On
Fiber is the biggest thing to reduce. High-fiber foods like whole grain bread, brown rice, bran cereals, raw vegetables, beans, and lentils take longer to digest and can cause bloating, gas, or cramping during your run. The Gatorade Sports Science Institute recommends avoiding high-fiber foods for at least 24 hours before competition, and possibly longer if you’re prone to stomach issues. Choose processed white grains over whole grains, peel your fruit, and cook your vegetables. A few naturally low-fiber options include zucchini, tomatoes, olives, grapes, and grapefruit, all with less than one gram of fiber per serving.
High-fat and high-protein foods should also take a back seat. A big steak dinner or a plate of fried food sits heavy in your gut and displaces the carbohydrates you need. Fat slows digestion, which is the opposite of what you want heading into a run. Keep protein portions modest and choose lean options.
Milk and dairy products are worth watching carefully. Lactose is the most commonly removed food group among athletes who experience GI problems during exercise. If you know dairy doesn’t bother you, yogurt and low-fat milk are fine carbohydrate sources. If you’re unsure, the day before a race is not the time to test it.
Foods That Can Cause Stomach Problems
Some runners have sensitive digestive systems that react to a group of fermentable sugars found in everyday foods. Honey, cherries, and watermelon contain more fructose than glucose, which can trigger bloating and abdominal pain in susceptible people. Garlic, onions, and certain legumes fall into the same category. If you’ve ever had unexplained stomach trouble during a run, reducing these foods in the day or two before your event could help.
Spicy food is another common trigger. It won’t affect your glycogen stores, but it can irritate your gut and lead to discomfort during exercise. The general rule for the day before a run is to eat familiar, bland, well-tolerated foods. Nothing new, nothing adventurous.
Skip The Alcohol
A beer or glass of wine the night before a run does more harm than most people realize. Research published in the Journal of Applied Physiology found that alcohol consumed after exercise cut muscle glycogen restoration nearly in half over an eight-hour recovery window. Even at the 24-hour mark, glycogen stores were still measurably lower compared to when no alcohol was consumed. That means drinking the night before directly undermines the carb-loading you’ve been doing all day. If you’re serious about performing well, skip it entirely.
Hydration Without Overdoing It
Drink water consistently throughout the day rather than chugging large amounts all at once. Your urine should be pale yellow by the evening. Sports drinks can serve double duty here, contributing both fluid and extra carbohydrates toward your daily target. Avoid drinking so much that you feel waterlogged or wake up repeatedly during the night.
Shorter Runs Need Less Preparation
All of this advice scales with the length and intensity of your run. If you’re preparing for a half marathon, marathon, or any run lasting 90 minutes or more, full carbohydrate loading makes a real performance difference. For a casual 5K or a regular training run under an hour, you don’t need to overhaul your diet. Just eat a normal, balanced dinner with a good portion of carbs, avoid anything you know upsets your stomach, and you’ll be fine. The 10 to 12 grams per kilogram recommendation is specifically designed for endurance events where glycogen depletion is a real risk.