When preparing your fueling strategy for an endurance event, your priority should be understanding how much carbohydrate you need to consume per hour to sustain your performance.
Athletes often ask us if there’s an optimal way to hit those hourly carb targets during exercise - should you eat a little and often? Or gulp a single gel down every hour?
I’ve taken a look at what the science and practical experience tell us about the optimal dose and frequency for eating and drinking during exercise…
Little and often vs down in one...
If you’re working at a moderate-to-high intensity, carbohydrates are a crucial energy source as fat metabolism alone can't typically deliver energy quickly enough to meet the demands of this effort level.
The body stores carbs as glycogen in the muscle and liver, but these reserves are limited. Once depleted, performance can decline rapidly, resulting in fatigue, reduced power output, and an increased perception of effort.
So, you’re going to need to fuel during exercise to maintain your performance. How many grams of carb you need per hour to perform at your best will be dictated by the intensity and duration of your event.
You can use the free Fuel & Hydration Planner to get a nutrition plan for your next race, including the carb numbers you should ideally be aiming to hit...
Most athletes require about 60-90g of carb hour, but it's also worth considering how you’re going to hit those carb numbers. Will you use gels, chews, bars, drink mixes, or real foods, or a combination of all of them?
Taking it a step further, how frequently will you fuel? Having a strategy for how much (and how often) you’re going to eat and drink each hour could have a significant impact on your ability to hit your carb targets…
Taking larger doses in one go - especially doses exceeding 60 grams in one hit - could overload intestinal transporters, slow gastric emptying, and increase the risk of gut issues.
In contrast, consuming smaller, more frequent doses seems to support better digestion by allowing the gut to continuously process carbs without becoming overwhelmed.
This was highlighted in a study examining different carb feeding strategies during exercise. Researchers found that frequently consuming small volumes of carb helped to maintain steady ‘intragastric pressure’ (pressure inside the stomach), and resulted in better gut comfort, compared to consuming them in one large hit.
Oxidation efficiency (i.e. the proportion of carbs you ingest that are then burned to generate energy) can also be affected by how often you consume your gels, chews and drinks.
A group of researchers at Loughborough University investigated the impact of fueling frequency by putting 12 well-trained male runners through two 100-minute treadmill runs at ~70% of their V̇O₂ peak.
The athletes consumed the same total amount of carb (1 litre of fluid containing ~100g of carbs) during each run. The only difference between trials was the dosing strategy:
- One delivered moderate doses less frequently (i.e. 5 moderate doses of 20g delivered as 200ml every 20 minutes)
- The other delivered smaller doses more frequently (i.e. 20 small doses of 5g delivered as 50ml every 5 minutes)
Interestingly, the researchers found that the less frequent, moderate doses led to higher exogenous carb oxidation rates than the more frequent, smaller doses.
These results suggest that moderate doses of carb may improve gastric emptying and intestinal absorption, thereby enhancing the oxidation of ingested carbs. So, a moderate dose every 20 minutes may give you the most ‘bang for your buck’.
Another study found that smaller, more frequent doses - which they defined as 20-30g every 15-20 minutes - can help stabilise blood glucose and reduce GI discomfort; both of which may support higher carb intakes over time.
So, the science suggests that small-to-moderate doses taken relatively frequently are optimal, but it’s worth considering the best approach for you…
How frequently should you fuel?
During the course of analysing hundreds of athletes’ race nutrition strategies and publishing Case Studies, we’ve witnessed a wide range of carb-dosing strategies.
Using an example of an athlete trying to hit 90g of carb per hour, I’ve outlined five of the most common patterns of carb intake that we see…
1. Large, infrequent doses (i.e. 90g of carb in one go each hour)
For athletes who prefer a simplified fueling approach, taking all of your carbs in one go on the hour can seem appealing. This reduces the need to monitor your intake so often as you hit your carb numbers in one ‘hit’, on the hour, every hour.
But, research suggests that this strategy could lead to spikes and crashes in blood glucose levels, leading to inconsistent energy availability and increased GI distress.
2. Moderate Frequency (i.e. 45g of carb every 30 minutes)
A more balanced fueling approach involves dividing your hourly carb intake into two doses (e.g. 45g every 30 minutes to meet a 90g/h target).
Ultrarunner Robbie Britton hits 90g/h by consuming a PF 90 Gel in two separate doses. “My method is a big gulp initially and then I finish whatever is left in another hit by the end of the hour.”
3. Frequent Intake (i.e. 30g of carb every 20 minutes)
Taking in smaller amounts of carbs every 20 minutes, helps smooth out energy delivery and reduce the risk of GI distress.
Research suggests that this approach enhances carb oxidation rates and supports more stable glucose levels over time. We’ve seen from our Athlete Case Studies that this is a common strategy across sports.
For example, due to the logistics of ultramarathon swimming and wanting to avoid having to stop mid-swim, world record-breaker Andy Donaldson takes a carb-feed from his support boat every 20 minutes to keep his energy levels up. “I stick to my plan and feed every 20 minutes.”
Top tip: Consider setting an alarm on your phone or watch to remind you to eat and / or drink at set intervals.
4. Drip-Feeding (i.e. 15-20g every 10-15 minutes)
Some endurance athletes adopt a drip-feed approach, consuming small amounts of carb every 10-15 minutes.
This method is ideal for minimising GI distress over long periods of time and could be an effective strategy in ultra-endurance events where maintaining a steady, uninterrupted fuel supply is crucial.
Research highlights that gut training can improve an athlete’s ability to absorb small, frequent carb doses, reducing the risk of discomfort on race day.
Ultrarunner Caleb Olson says; “I’m a little-and-often kind of guy. I take a quarter of the PF 90 Gel every 15 minutes.”
5. Continuous Sipping (i.e. every 5 minutes)
At the most frequent end of the spectrum, some athletes might choose to sip small amounts of carb every few minutes. This method would provide a near-continuous energy supply, closely mimicking the body’s natural energy needs, avoiding spikes or crashes in blood glucose.
But it requires constant access and ability to fuel, which isn’t practical in every race scenario, especially where focus is needed. It’s not something we’ve seen commonly across our Athlete Case Studies.
To help give you a practical guide to consider how you might hit your hourly carb targets, the graphic below gives a breakdown of different intake patterns. These examples can help guide your planning and give you a sense of how flexible your carb dosing strategy could be.
4 factors that influence carb dosing
How you consume your carb targets each hour will depend on a range of factors, including gut tolerance, race intensity, logistics, and personal preference. Just as training your gut to tolerate the volume of carbs is important, testing different patterns in training is the best way to discover what works for you.
Before committing to a set strategy, it’s worth considering how your approach might be impacted on race day…
1. Type of sport
Cycling: Frequent fueling (every 10-15 minutes) is generally easier to implement. Athletes can access bottles, gels and food without slowing down or stopping, making it ideal for a drip-feed approach.
Many professional cyclists consume a gel, chew or take a drink every 15 minutes to hit their high carb targets of 90-120g/h.
Additionally, the course profile and elevation may affect your fueling strategy. It’s often more difficult to eat whilst descending or riding on technical sections.
Running: Runners tend to favour compact, easy to carry fuel sources like gels, chews or carb drinks, taken at regular intervals.
Fueling every 20-30 minutes is often more practical because how much you’re able to carry can be limited during marathons and ultramarathons. Plus, the high-impact nature of running can negatively affect digestion and make consuming carbs more difficult.
A study monitoring participants in a 100-mile ultramarathon found that those who consumed carb more frequently had better glucose control and improved performance outcomes.
Triathlon: Fueling frequency typically varies by discipline. Athletes often adopt a drip-feed approach during the bike leg where fueling is easier, and gut tolerance is usually higher. And then shift to a less frequent pattern (e.g. every 20-30 minutes) on the run, where digestion becomes more sensitive and logistics can be more complicated.
2. Gut comfort
If you're prone to gut issues, then smaller, more frequent doses of carb are generally better tolerated and can help reduce the risk of discomfort during exercise.
It’s also worth doing some gut training during key training sessions to help increase your tolerance to your ideal carb intake and practise how you plan to consume your carbs on race day.
3. Exercise intensity and duration
High-intensity efforts (e.g. interval sessions and faster marathons): Liquid carbs are often preferred because they're faster to absorb and easier to digest under stress. At higher intensities, the gut is under more strain, so carb-rich drink mixes are often more effective.
Ultra-endurance races: At lower intensities, athletes can often tolerate a wider variety of fuels, including solid foods. Incorporating bars, chews and real foods into your plan during these longer events can provide a welcome change of texture and help to avoid flavour fatigue, which can be crucial when you’ve been regularly eating a single source of carbs for hours on end.
Of course, eating a bar or a sandwich in one go is much more difficult and a slower affair than slurping down a gel, so factor this into your dosing strategy.
4. Environmental conditions
Environmental factors can also influence gut comfort. In hot and humid conditions, sweat rates increase and more blood is redirected to the skin for cooling, which reduces blood flow to the gut. This can heighten the risk of GI discomfort, so small, frequent doses of carbs are often the preferred dosing strategy in these environments.
On the flip side, cold conditions can make it difficult for you to open gels and packets on the move. This may well impact how often you’re able to fuel, so plan ahead by removing chews and bars from packets and make them easily accessible for you to eat on the move.
Naturally, you're likely to drink less when it's cold too, so avoid relying solely on your bottles to hit your carb numbers. Consider adding more solid fuel sources to your plan in cold weather.
A carb dosing case study
The key is to take some time to find a fueling frequency that works for you and your sport. I spoke to pro triathlete and adventure racer, Dougal Allan, to find out how he’s refined his optimal carb dosing strategy after years of racing a variety of sporting disciplines…
“While carbohydrates come in many forms, I found that sports-specific nutrition products like energy gels, chews and drinks are the most efficient way to get carbs on board when I’m breathing heavily and working at a high intensity during training and races. They tend to sit better in my stomach compared to more solid or fibrous food options, whether I'm running, swimming, cycling, or kayaking.
When it came to working out how often to fuel during adventure races, one of my early breakthroughs came when I realised how my digestive system responded to different forms of exercise. In particular, my ability to tolerate carbohydrate intake varied depending on the sport.
- Running presented the greatest challenge. I struggled to ingest more than 70-90 grams of carbohydrate per hour without discomfort
- Kayaking, on the other hand, allowed me to consume 120 grams or more per hour quite comfortably
I hypothesised that this variation might be due to mechanical stress on the digestive system - specifically the bouncing motion of running versus the relatively stable seated posture in kayaking, which could reduce gastrointestinal strain.
In practice, I found the most effective strategy involved consuming a gel or chew every 20–30 minutes, and drinking 500–1000ml (~16-32oz) of sports drink per hour, depending on the environmental conditions and intensity. This provided a total intake of approximately 70-120 grams of carbs per hour.
Interestingly, I discovered that consuming full servings (e.g. an entire gel or several larger sips of sports drink) at set intervals helped combat flavour fatigue. Taking small amounts more frequently tended to leave a lingering taste in my mouth, which became unpleasant over time. Larger, less frequent doses were easier to manage both physically and mentally.
One final and perhaps underrated advantage of this system was how easy it was to quantify and manage while racing. For example:
- 1 PF 30 Gel = 30g of carb
- 1 bottle of Carb Only Drink Mix (at my preferred concentration) = 90g of carb per litre
This simplicity became crucial during long events, when cognitive performance often declined due to fatigue and reduced blood flow to the brain. Having clear, easy-to-track fuelling metrics ensured that I could stay on target even when mental clarity was compromised.”
Key takeaways
Ultimately, your optimal dose and frequency will come down to what works best for you.
In general, smaller, more frequent doses (every ~20 minutes) provide a more ‘stable’ energy supply and reduce gut issues. The key is to personalise your plan based on your gut tolerance, race demands, conditions, and personal preference.
Test out what works best for you during key training sessions. Consider using an alarm on your phone or watch to remind you to eat and / or drink at set intervals to ensure you keep hitting your carb numbers (which could be very important when monitoring your intake becomes more difficult as you become physically and mentally fatigued during long events).
If frequent fueling during your event is difficult, fueling well beforehand becomes even more important. Carb-loading 24-48 hours before your race can help maximise muscle glycogen, supporting sustained energy and delaying fatigue.
Use our free Fuel & Hydration Planner to calculate your ideal carb intake, then book a free Video Consultation to fine-tune your strategy with our Athlete Support Team.
