Training for a half marathon demands more from your body than casual running, and your diet needs to match. The core principle is straightforward: eat enough carbohydrates to fuel your training, enough protein to recover from it, and time your meals so your stomach cooperates on run days. Here’s how to put that into practice across your training cycle.
Daily Carbohydrate Needs
Carbohydrates are your primary fuel source during running. Your muscles store them as glycogen, and a hard training run can drain those stores significantly. For general training needs, aim for 5 to 7 grams of carbohydrate per kilogram of body weight each day. During heavier training weeks or when your long runs stretch past 90 minutes, that range climbs to 7 to 10 grams per kilogram.
For a 150-pound runner (about 68 kg), that translates to roughly 340 to 475 grams of carbohydrate on standard training days. In practical terms, that’s a lot of rice, oatmeal, bread, pasta, potatoes, fruit, and cereal. If you’re consistently feeling flat or sluggish on runs, undereating carbohydrates is one of the first things to check.
Protein for Muscle Repair
Running breaks down muscle tissue, especially during longer efforts. You need protein to rebuild it. Current evidence suggests endurance athletes should target about 1.8 grams of protein per kilogram of body weight on standard training days. On rest days, that number actually increases slightly to around 2.0 grams per kilogram, because your body is doing the bulk of its repair work.
For that same 150-pound runner, this works out to roughly 120 to 135 grams of protein per day depending on the training phase. Spread it across meals rather than loading it all into dinner. Research on endurance athletes points to roughly 0.5 grams per kilogram per meal as the amount that best stimulates muscle protein repair. That’s about 34 grams per meal for a 68 kg person, which looks like a chicken breast, a cup of Greek yogurt with nuts, or a couple of eggs alongside some cottage cheese.
Women in the luteal phase of their menstrual cycle (the two weeks before a period) may benefit from bumping protein slightly higher, closer to 1.9 grams per kilogram per day, to offset hormonal shifts that can increase muscle protein breakdown.
What to Eat Before a Long Run
Your pre-run meal serves one purpose: topping off glycogen stores without upsetting your stomach. Eat a carbohydrate-rich meal 2 to 4 hours before your run. The closer to your run you eat, the smaller and simpler the meal should be. A bowl of oatmeal with banana works well three hours out. If you’re eating just 60 to 90 minutes before, stick to something easy to digest: a slice of toast with jam, a handful of dry cereal, or half an energy bar.
The foods most likely to cause stomach trouble during running are high in fat, fiber, or both. Endurance runners commonly avoid meat, milk products, legumes, high-fiber vegetables, and chocolate in the hours before a run. These foods slow digestion, and when blood flow shifts away from your gut and toward your legs, anything sitting heavy in your stomach can cause cramping, bloating, or worse. Training runs are the time to experiment with your pre-run meals so you know exactly what works before race day.
Fueling During Runs Over 90 Minutes
For shorter training runs, water is usually enough. Once your runs stretch past 90 minutes, you need to take in carbohydrates while running. The target is 30 to 60 grams of carbohydrate per hour. That’s the equivalent of one to two energy gels, a few handfuls of sports chews, or 16 to 32 ounces of a sports drink.
Your gut needs training for this just like your legs do. Many runners find that taking in calories mid-run causes nausea or cramping at first. Start with small amounts early in your training plan and gradually increase. By the time your long runs hit 10 to 12 miles, you should have a fueling strategy that your stomach tolerates well. Whatever you plan to use on race day, practice with it during training. Switching to a new gel or drink on race morning is a common mistake.
Post-Run Recovery Meals
After a hard or long run, your muscles are primed to absorb nutrients and begin rebuilding. The old idea of a strict 30-minute “anabolic window” has softened. What matters more is that your pre-run and post-run meals aren’t separated by more than about 3 to 4 hours total. If you ate a solid meal two hours before a 75-minute run, you have some flexibility. If you ran fasted first thing in the morning, eating soon afterward becomes more important.
A good recovery meal combines carbohydrates to replenish glycogen with protein to start muscle repair. A peanut butter sandwich with a glass of milk, a smoothie with fruit and protein powder, rice with chicken and vegetables, or eggs on toast all fit the bill. If you struggle to eat solid food immediately after running, a small smoothie or chocolate milk can bridge the gap until your appetite returns.
If your stomach can’t handle much food after a hard effort, prioritizing protein at about 0.4 grams per kilogram of body weight can help compensate for lower carbohydrate intake in that initial recovery period. For most runners, that’s roughly 25 to 30 grams of protein, or about one cup of Greek yogurt.
Staying Hydrated
Dehydration of more than 2% of your body weight during exercise measurably hurts performance. For a 150-pound runner, that’s just 3 pounds of fluid loss, which can happen in under an hour on a hot day. The simplest way to monitor hydration is to weigh yourself before and after a few training runs. Every pound lost represents roughly 16 ounces of fluid you didn’t replace.
Before long runs, drink 5 to 10 milliliters per kilogram of body weight at least two hours beforehand. For a 68 kg runner, that’s about 12 to 24 ounces sipped over the two hours before you head out. This gives your body time to absorb the fluid and lets you use the bathroom before you start.
Sweat contains sodium, and if your runs are long or the weather is warm, plain water alone won’t fully replace what you lose. Average sweat sodium concentration is roughly 50 millimoles per liter, though individual variation is enormous. Some people are light salt sweaters, others leave white streaks on their shirts. If you notice salt residue on your skin or clothing after runs, or if you get muscle cramps late in long efforts, adding an electrolyte drink or salt tabs to your fueling plan is worth trying.
A Typical Training Day Plate
Putting all of this together, a standard training day for a half marathon runner might look like this:
- Breakfast (pre-run): Oatmeal with banana and a drizzle of honey, plus a glass of orange juice. High in easily digestible carbohydrates, low in fat and fiber.
- Post-run snack: A smoothie made with milk, frozen berries, and protein powder, or a peanut butter sandwich.
- Lunch: Rice bowl with chicken, roasted sweet potatoes, and a side of vegetables. A balance of carbohydrates and protein with moderate fiber.
- Afternoon snack: A bowl of cereal with milk, or toast with nut butter and jam.
- Dinner: Pasta with a meat-based sauce and a side salad. Another carbohydrate-heavy meal to continue restocking glycogen for the next day’s training.
On rest days, the overall structure stays similar, but you can ease off the carbohydrate volume slightly and let protein take a larger share of your plate. Rest days are when your body does its deepest repair work, so this isn’t the time to eat less overall. It’s just a shift in emphasis.
Foods to Limit During Heavy Training
You don’t need to follow a restrictive diet while training, but a few categories of food are worth being thoughtful about. Very high-fiber meals (large portions of beans, raw cruciferous vegetables, bran cereals) are best saved for rest days or eaten well away from run times. The same goes for rich, high-fat foods. A burger and fries the night before a long run won’t ruin your training, but a pattern of heavy meals close to runs will eventually catch up with your gut.
Alcohol deserves a mention too. It impairs glycogen replenishment, disrupts sleep quality, and acts as a diuretic. An occasional beer won’t derail your training, but regular drinking during a training cycle makes recovery harder in ways that compound over weeks. If you’re going to drink, do it on rest days and well before your next run.