A long run can expose a difficult choice: should you run with little or no fuel to become more efficient, or practice taking gels so race day feels familiar? If you are wondering whether to practice marathon fueling on long runs, the practical answer is to do both strategically—but not in equal amounts.
Fasted or lightly fueled running can have a place in an easy training week. However, saving all race fueling for race day is a poor plan. Your stomach, pacing strategy, carbohydrate intake, and hydration routine all need practice before the marathon. For many runners, long runs are the safest place to build toward roughly 60–90 grams of carbohydrate per hour when the session and race goals justify it.
Quick Answer
Practice marathon fueling on long runs. Do not wait until race day to test gels, drinks, timing, or the amount of water you need with them.
Use fasted or lightly fueled running selectively for short, easy sessions if you tolerate it and it does not reduce training quality. It should not replace fueling for demanding long runs, marathon-pace work, hot-weather training, or sessions lasting several hours.
A useful progression is:
- Start with 30–45 grams of carbohydrate per hour on long runs.
- Increase gradually toward 60 grams per hour as your stomach adapts.
- Consider 60–90 grams per hour for longer or faster marathon efforts, especially when using products designed with multiple carbohydrate sources.
- Rehearse the exact products, timing, fluids, and caffeine plan you expect to use in the race.
The goal is not to prove that you can suffer without food. The goal is to arrive at the marathon able to maintain pace, absorb fuel, and avoid preventable surprises.
Why This Happens
Fasted-training advice often comes from a real physiological observation: exercising with lower carbohydrate availability can increase the contribution of fat to energy production. That does not mean every long run should be performed without fuel, or that fat adaptation automatically improves marathon performance.
A marathon is still heavily dependent on carbohydrate. Stored muscle glycogen is limited, and the faster you run, the more heavily you generally rely on carbohydrate. Starting with full glycogen stores and replacing some carbohydrate during the race can help preserve pace late in the event. Fuel also supports the quality of marathon-pace segments and long runs that are meant to prepare you for race fatigue.
There is another issue that gets overlooked: gut training. Taking a gel while running is a learned skill. You must open the packet, swallow it while breathing hard, manage the texture, and drink enough fluid to reduce the chance of stomach discomfort. Your digestive system also needs repeated exposure to carbohydrate during exercise. A product that seems fine at rest may feel unpleasant at mile 20 if you have never practiced with it.
Race-day-only gels create several risks:
- You may choose a product that is too thick, sweet, acidic, or difficult to digest.
- You may take too much carbohydrate at once because you have not practiced timing.
- You may discover that a gel requires water, but the next aid station is still far away.
- You may use caffeine for the first time during a stressful, dehydrating event.
- You may underfuel because you are afraid of stomach problems.
Fasted running also has a cost when used at the wrong time. A low-carbohydrate long run can make the final miles slower and more stressful than intended. If it compromises recovery, sleep, or the next quality workout, the experiment may reduce the overall value of your training week.
Step-by-Step Method
1. Decide what the run is supposed to train
Before choosing your fuel, identify the purpose of the session. An easy 60-minute run, a three-hour endurance run, and a long run with 10 miles at marathon pace do not have the same fueling needs.
For a short, relaxed run, normal daily meals may be enough. For a long run designed to simulate race demands, practice fueling deliberately. If the workout includes sustained marathon pace, hills, heat, or a high weekly training load, prioritize performance rather than restricting carbohydrate.
2. Eat a normal pre-run meal
Do not confuse an overnight fast with poor preparation. A long run should usually begin after a familiar meal or snack that provides carbohydrate and sits comfortably in your stomach.
Many runners use a carbohydrate-focused breakfast one to three hours before starting. The exact amount depends on body size, timing, tolerance, and the workout. Common options include toast with banana, oatmeal, a bagel, cereal, or a sports drink. Avoid testing a large, high-fat, high-fiber meal before a key run.
3. Start with a manageable carbohydrate target
If you rarely fuel during runs, begin with about 30–45 grams of carbohydrate per hour. This could be one gel every 30–40 minutes, depending on the label, or a combination of sports drink and chews.
Take the first serving before you feel depleted. For many runners, 20–30 minutes into the run is easier than waiting until hunger, weakness, or heavy legs appear. Early, regular intake is usually more comfortable than trying to catch up late.
4. Build toward your marathon target gradually
Increase the amount over several long runs rather than jumping from zero to 90 grams per hour. A simple progression might look like this:
| Training phase | Long-run fueling target | Main purpose |
|---|---|---|
| First experiments | 30–45 g/hour | Learn timing and product tolerance |
| Regular long runs | 45–60 g/hour | Support endurance and build gut familiarity |
| Race-specific workouts | 60–90 g/hour if tolerated | Rehearse marathon demands |
| Easy short runs | Optional or minimal | Avoid unnecessary fueling rules |
The upper range is not mandatory for every runner. Some people perform well with less, while others benefit from more. Product concentration, running duration, intensity, body size, weather, and total pre-run carbohydrate all matter.
5. Match fluids to the product
Check the nutrition label. Some gels are designed to be taken with water, while isotonic gels contain more fluid and may not require the same amount. Taking a thick gel without enough water can increase the chance of a sticky mouth or stomach discomfort.
Do not force large amounts of plain water to compensate for high carbohydrate intake. Drink according to thirst, conditions, sweat losses, and your race plan. In hot weather or for heavy sweaters, sodium and fluid planning may also deserve attention, but avoid copying another runner’s exact routine.
6. Practice the race schedule, not just the food
Write down when you expect to take fuel during the marathon. For example, you might take a serving around 20–30 minutes, then repeat at regular intervals. Adjust the schedule so it fits aid stations and avoids taking several products together.
Use the same packet size, flavor, caffeine level, and carrying method when possible. Practice opening gels while wearing the clothing and hydration gear you expect to race in. Small logistical problems become much more annoying after two hours of running.
7. Evaluate the result after the run
Record four things: pace, energy, stomach comfort, and recovery. If you felt good but had bloating, try more water or a smaller serving. If your stomach was fine but your energy faded, increase the frequency or total carbohydrate. If the run felt unusually hard, check sleep, heat, pacing, and pre-run food before blaming the fuel.
A successful fueling plan is repeatable. One lucky run proves very little; three or four comfortable rehearsals provide much better evidence.
Common Mistakes
Saving every gel for race day
This is the biggest mistake. A marathon is too long and too consequential to be the first product test. Use long runs to identify flavors, textures, caffeine tolerance, timing, and fluid needs instead.
Treating fasted training as a toughness test
Running without fuel is not automatically more productive. If the session becomes slow, chaotic, or difficult to recover from, it may interfere with the rest of your plan. Use low-fuel runs only when the workout is easy and the downside is small.
Taking one large dose after feeling tired
Waiting until you are exhausted can lead to a large, rushed intake that upsets your stomach. Start earlier and take smaller servings at regular intervals.
Copying a 90-gram target immediately
More carbohydrate is not always better if your digestive system is not prepared. Build gradually. Also remember that some gels contain 20–30 grams per serving, while others contain more, so count grams rather than packets.
Testing caffeine on race morning
Caffeine can affect alertness, heart rate, anxiety, and digestion. If you plan to use caffeinated gels, introduce them during training and account for coffee, tea, energy drinks, or other sources.
Ignoring the rest of the training week
A long run performed underfueled may look impressive but damage the next workout. Training adaptation depends on the entire week. Fuel the sessions that need quality, and do not turn every run into a metabolic experiment.
Checklist or Decision Table
Use this table before deciding how aggressively to fuel a long run:
| Run situation | Recommended approach | Why |
|---|---|---|
| Easy run under 60 minutes | Normal meals; fuel usually optional | The session is short enough for many runners to complete comfortably |
| Easy run lasting 90 minutes or more | Begin practicing regular carbohydrate | Builds routine before fatigue becomes severe |
| Long run over two hours | Fuel consistently, often 45–75 g/hour | Supports pace, recovery, and gut training |
| Marathon-pace workout | Use the planned race strategy | The goal is to rehearse race-specific demands |
| Hot or humid long run | Fuel and plan fluids more carefully | Heat increases overall stress and can change tolerance |
| First run testing a new gel | Use a low-risk easy route | Makes it easier to stop if your stomach reacts |
| Runner with recurring stomach symptoms | Reduce complexity and review the plan | Product type, concentration, pacing, and medical issues may all matter |
A practical decision rule is: if the run is long, fast, hot, or important, fuel it. If it is short and easy, you have more freedom to run with little or no mid-run carbohydrate.
When This Advice Does Not Apply
Not every runner should chase 60–90 grams per hour. That range is a performance-oriented guideline, not a requirement or a guarantee. Smaller runners, slower runners, and people completing shorter events may use less. A qualified sports dietitian can help personalize intake when performance goals, gastrointestinal problems, diabetes, or other health conditions complicate the decision.
Do not use fasted running to compensate for disordered eating, chronic under-fueling, or pressure to lose weight. Low energy availability can harm recovery, hormones, bone health, mood, and performance.
Stop a run and seek appropriate medical advice for chest pain, fainting, confusion, repeated vomiting, severe weakness, or symptoms that do not improve with rest and normal hydration. Persistent abdominal pain or recurring exercise-related diarrhea also deserves professional evaluation rather than endless gel experimentation.
Finally, do not change your full race plan based on one bad training run. Heat, pace, nerves, poor sleep, and an overly concentrated drink can all cause trouble. Look for patterns and adjust one variable at a time.
Realistic Example
Consider a runner preparing for a four-hour marathon who usually takes no fuel on long runs. Their first step is not to carry six different gels and attempt 90 grams per hour. Instead, they eat a familiar breakfast, carry one gel and a sports drink, and aim for about 35–40 grams per hour on a two-hour easy run.
That run goes well, but the gel feels thick without water. On the next long run, the runner takes it at 25 minutes with water, then repeats the same routine later. After two comfortable runs, they add a second carbohydrate source and reach about 55–60 grams per hour during a marathon-pace session.
By the final race-specific long run, they have tested the actual products, timing, bottle placement, and caffeine choice. They may still adjust the target on race day, but they are no longer solving basic fueling problems at mile 20.
Final Takeaway
Practice marathon fueling on long runs, but progress toward your target instead of copying an advanced intake immediately. Use fasted or lightly fueled running only for selected easy sessions, not as a replacement for race-specific preparation.
The best plan is the one you can absorb, repeat, and match to the marathon. Start early, take smaller regular servings, pair products with appropriate fluids, and rehearse the entire routine before race day.
FAQs
Should I run my long runs without gels to improve fat burning?
You can occasionally run an easy, shorter long run with little or no mid-run fuel if you tolerate it, but you do not need to do this to become a better marathoner. Fat use may increase when carbohydrate availability is lower, yet marathon performance still depends heavily on carbohydrate and training quality. If running unfueled makes you slow down sharply, feel unwell, or struggle to recover, the cost is probably too high. Keep low-fuel sessions controlled and fuel long, fast, or race-specific workouts.
When should I take my first gel during a marathon long run?
Take your first gel about 20–30 minutes into the run rather than waiting until you feel empty. Early intake gives your body time to absorb carbohydrate and makes it easier to maintain a steady supply. Use the product label to determine whether you need water, and begin with a manageable amount if you are new to fueling. You can then repeat servings at regular intervals, often every 25–40 minutes, depending on the carbohydrate content and your hourly target.
Is 60–90 grams of carbs per hour necessary for marathon training?
No, 60–90 grams per hour is not necessary for every runner or every long run. It is a useful upper-range target for some longer, faster, or race-specific sessions, particularly when the runner has gradually trained their gut. Many runners begin successfully with 30–45 grams per hour and progress toward 45–60 grams. Your pace, duration, body size, product type, weather, pre-run meal, and tolerance all influence the right amount. Consistency and comfort matter more than chasing a number.
How can I train my stomach to tolerate gels while running?
Train your stomach by introducing one product at a time, starting with a small and regular carbohydrate dose during easy running. Take the gel before you are severely tired, use the recommended water, and repeat the test across several runs. Avoid combining a new gel, high caffeine dose, unfamiliar sports drink, and aggressive pace in one workout. If symptoms appear, change one variable at a time. Persistent or severe gastrointestinal symptoms should be discussed with a qualified medical professional or sports dietitian.
Can I use race-day gels only during my marathon long runs?
You should use the same race-day gels during several long runs before the marathon, not save them for the event. Practice confirms that the flavor, texture, caffeine, packaging, and required fluid work for you under fatigue. You do not need to use the exact race product on every easy run, but include it in key race-specific sessions. Also practice carrying it and opening it while moving. Familiarity reduces both stomach risk and logistical mistakes on race day.
What should I do if gels upset my stomach on long runs?
First, check whether you took too much carbohydrate at once or failed to drink enough water with a concentrated product. Slow the pace, simplify the fuel, and test a smaller serving or a different texture on an easy day. Avoid introducing caffeine and multiple new products together. Heat, dehydration, fast pacing, and high fiber or fat before running can also contribute. If nausea, pain, vomiting, or diarrhea keeps recurring despite sensible adjustments, seek professional guidance rather than forcing more gels.