Marathon Fueling Guide: How Many Carbs, Gels & When

For any run longer than about 75 minutes, aim to take in 30 to 60 g of carbohydrate per hour, starting within the first 30 to 40 minutes, and sip fluid to thirst with some sodium. Trained runners can build toward 90 g per hour with a glucose and fructose blend. Carb-load for the final one to three days before a marathon, and never try a new fuel on race day.

Why Fueling Matters: Glycogen and the Wall

Your muscles run mostly on glycogen, a store of carbohydrate that is surprisingly small. The commonly cited figure is that it covers somewhere around 90 minutes to two hours of hard running, depending on your fitness and pace. When it runs low, your pace falls and everything feels heavier, which is what runners call hitting the wall. It is less a mystery than a fuel gauge reaching empty.

Fat can supply a lot of energy, but it cannot be burned fast enough to hold marathon pace on its own. That is why the plan is not to avoid the wall by running slower, but to top up the tank as you go. Fueling does two jobs: it delays the point where stores run out, and it keeps your brain and legs feeling better in the late miles.

Carbs per Hour: The 30, 60, 90 Scale and Gut Training

Sports-nutrition guidance converges on a range rather than a single number. Around 30 to 60 g of carbohydrate per hour is the baseline for most runners. Your gut can absorb only so much glucose at once, which is why intakes above roughly 60 g per hour usually use a blend of glucose and fructose, which travel through different absorption routes. For efforts beyond about two and a half hours, guidance for trained athletes goes up to around 90 g per hour with that blend.

The key word for the top end is trained. Your gut adapts to carbohydrate in the same way your legs adapt to mileage, and the fastest way to make it fail on race day is to ask it for something it has never done. Gut training is simply practising your race fueling on your long runs, increasing the amount gradually over several weeks, until your stomach handles the target without complaint.

• Start with what you can tolerate, often around 30 to 40 g per hour, and add roughly 10 g per hour every week or two.
• Use the same products, the same timing, and the same fluids you plan to use on race day.
• Treat a stomach problem as data, not failure. Change one thing at a time: the amount, the product, or the gap between doses.
• Be cautious above 90 g per hour. The evidence there is stronger in cycling than in running, and the gut issues are more common.

Before the Run: The Pre-Run Meal and Timing

The aim of a pre-run meal is to top up liver glycogen after the overnight fast, not to stuff yourself. A reasonable rule of thumb is a carbohydrate-rich meal one to four hours beforehand, then a smaller, simpler snack if you are cutting it fine. The closer to the start, the less fat, fibre, and protein you want in it.

• Three to four hours before: a full meal built on carbs, such as rice, bread, or oats, with a little protein. In an Indian kitchen, that can be rice with dal, or two or three idli with sambar.
• One to two hours before: a smaller, low-fibre meal, such as a banana with toast, a bowl of oats, or a cup of poha.
• Under 30 minutes before: only a few sips of a carb drink or a small piece of fruit, if you tolerate it.

For easy-to-source options that suit Indian kitchens, here are rough carbohydrate values to plan with: 1 cup of poha is about 35 to 40 g, 2 idli about 25 to 30 g, 1 medium banana about 25 to 27 g, and 1 katori of cooked rice about 40 g. Our Indian runner's fueling guide has the full list and meal ideas by run length.

How Many Gels Do You Need in a Marathon? Fueling During the Run

Start fueling early, within the first 30 to 40 minutes, and take small amounts regularly rather than a big dose when you already feel empty. By the time you feel hungry or flat, you are behind. A steady rhythm, such as a small amount every 20 to 30 minutes, usually works better than one large hit at the hour mark.

Gels are popular because they are compact and predictable, and most contain about 20 to 25 g of carbohydrate, but you should check the label because it varies. Chews, sports drinks, and real food such as dates or banana all work, provided they are easy to carry and eat while moving. Here is a rough guide to how many gels a marathon might need.

These figures are a starting estimate, not a prescription. Your sweat rate, the weather, your gut tolerance, and how much comes from sports drink all change the answer, so use the table as a starting point and adjust it in training.

• Take gels with water rather than with a sports drink, otherwise the sugar concentration in the gut can get too high.
• Plan where you will fuel, not just how much. Know where the aid stations are, and carry your own gels or a soft flask if you do not trust the course drink.
• Use your long runs as rehearsals. If a product gives you trouble in training, it will give you trouble at mile 20.

Real food works in training too. Three to four pitted dates give roughly 25 to 30 g of carbohydrate and a tablespoon of jaggery about 18 g, which makes them cheap, portable alternatives to gels on long runs. Our Indian runner's fueling guide covers how to carry them and what to pair them with.

Carb-Loading the Final 72 Hours

Carb-loading raises your starting glycogen stores so you have more fuel in the tank at the start line. The widely used protocol is roughly 10 to 12 g of carbohydrate per kg of body weight per day for the final 36 to 48 hours, and some sources quote a broader range of about 8 to 12 g per kg over one to three days. For a 70 kg runner, that is on the order of 700 to 840 g of carbohydrate a day at the top end, which is a lot of food.

The practical way to do it is to change what you eat rather than to eat more. Cut back on fat and fibre, swap in rice, bread, potatoes, noodles, and juice, and keep the portions comfortable. Expect to feel a bit heavy and to see the scale go up by a kilo or two, because each gram of stored glycogen carries water with it. That is normal and is a sign it worked, not a problem. In an Indian kitchen that usually means more rice and roti with less oil in the sabzi, khichdi, and juice, jaggery or a banana between meals.

• Cut fat, fibre, and anything unfamiliar. Plain and boring is the goal.
• Spread carbs across the day with snacks, rather than trying to eat huge meals.
• Do not rush the last meal. A moderate dinner the night before is better than a giant one.

If your goal race is a January event such as the Tata Mumbai Marathon, our Tata Mumbai Marathon training plan covers the course and the race-week approach, and this carb-loading window is the one to practise.

Fueling in Heat and Humidity: Hydration and Sodium

Hot, humid conditions raise your sweat rate and your fluid and sodium losses, and they make the gut more sensitive. In heat, you may need to start fueling earlier, take smaller and more frequent doses, and use sports drinks that supply both carbohydrate and sodium.

Drink to thirst rather than to a strict schedule. Overdrinking is a real risk, because taking in far more fluid than you lose can dilute blood sodium and cause hyponatremia, which is dangerous. Salty sweaters, who notice white salt marks on their kit, generally need more sodium than others, and your own long runs are the best place to learn which camp you are in.

For the pacing side of hot-weather racing, including dew point adjustments and acclimatisation, read our guide to marathon training in Indian heat and humidity.

Putting Your Fueling Plan Together

A good fueling plan is boring on race day because you have already done it many times. Build it from your long runs: choose a carbs-per-hour target, pick products and drinks you tolerate, rehearse the timing, and write it down so you are not deciding anything when you are tired.

• Eight to ten weeks out: start practising fueling on every long run.
• Four to six weeks out: raise your intake toward your race target and test your actual race products.
• Final two weeks: stop experimenting. Keep to what you know works.
• Race week: carb-load from the final one to three days, and set out your fuel the night before.

Fueling works alongside the rest of your build. Our complete marathon training plan guide covers how the long run, quality sessions, and taper fit together.

If a long run went badly and you suspect fueling, our guide to what a bad long run really means helps you tell fueling problems from fatigue or pacing.