When it comes to endurance performance, it can be challenging to know what type of carbohydrates you should be taking. Whether you're training for a 5K, preparing for a marathon, or tackling an ultra-endurance event, understanding the pros and cons of different carbohydrate delivery methods can make the difference between hitting the wall and achieving your personal best.

Recent scientific research has provided clearer insights into how different carbohydrate sources affect performance, gastrointestinal comfort, and practical application across various race distances. Let's examine the evidence behind gels, powders, bars, chews, and real food options to help you make informed fuelling decisions.

The Science of Carbohydrate Absorption

Before diving into specific sources, it's important to understand that the form of carbohydrate delivery doesn't significantly impact oxidation rates once absorbed. Research shows that whether you consume carbohydrates through gels, bars, or drinks, your body's ability to utilise them for energy remains relatively similar [1,2,3]. However, the speed of absorption, gastrointestinal tolerance, and practical considerations vary considerably between sources.

So let's break down the pros and cons of different types of carbohydrate sources for endurance exercise.

Energy Gels: The Quick-Hit Solution

Pros

Energy gels represent the gold standard for rapid carbohydrate delivery during endurance events. Most gels provide 20-30g of carbohydrates in an easily portable package that can be absorbed within 5-15 minutes of consumption.

Performance Benefits:

• Fastest absorption rate among solid/semi-solid options
• Minimal gastric emptying time
• Highly portable and convenient
• Precise carbohydrate dosing

Research Support

Studies demonstrate that gel consumption results in less gut discomfort compared to energy bars alone [4]. There hasn’t been a tonne of research done comparing gels to other forms such as chews etc. However, these are the most common used carbohydrate source for endurance based research.

MARCHON Fuel30 energy gel

MARCHON Fuel30 gels exemplify optimal gel formulation, providing 30g of carbohydrates in a 2:1 glucose-to-fructose ratio. This dual-source approach maximises absorption rates and can support carbohydrate oxidation rates of up to 90g per hour when used in combination with other sources.

More info on why a 2:1 ratio was chosen here.

Cons

• Can become monotonous during ultra-distance events
• Some athletes experience flavour fatigue (one reason we created an unflavoured gel to minimise this)
• May require adequate fluid intake for optimal absorption
• May cause gastrointestinal distress if consumed too frequently without proper training

Best Applications:

• Marathon racing (20-42km)
• High-intensity training sessions
• Time trials and shorter races where rapid energy delivery is crucial
• As part of a mixed-fuel strategy in ultra-events

Carbohydrate Powders and Sports Drinks

Pros

Liquid carbohydrate sources offer unique advantages, particularly in combining hydration with fuel delivery.

Performance Benefits:

• Fastest gastric emptying and absorption
• Simultaneous hydration and fuelling
• Customisable concentration
• Minimal chewing required during exercise

Research Insights: Studies show that liquid carbohydrates can be absorbed more rapidly than solid sources, making them ideal for maintaining steady energy levels throughout endurance events [5].

Cons

• Requires carrying larger volumes for equivalent carbohydrate content
• Flavour monotony over long distances
• Potential for over-dilution or concentration errors
• May not provide the psychological satisfaction of "eating"

Best Applications:

• Hot weather conditions where fluid needs are elevated
• Cycling events where carrying larger volumes is practical
• Swimming portions of triathlons
• Base fuelling strategy combined with solid sources

Energy Bars: The Substantial Option

Pros

Energy bars occupy a unique position in the fuelling spectrum, providing more substantial nutrition with slower, sustained energy release.

Performance Benefits:

• More diverse nutrient profile (often including protein and fat)
• Greater satiety and psychological satisfaction
• Sustained energy release over 30-60 minutes
• Often contain beneficial micronutrients

Research Findings

While bars take longer to digest than gels, they can provide more sustained energy release. However, research indicates that consuming bars alone may result in greater perceived exertion and gastrointestinal discomfort compared to gel and drink combinations [2]. However this will be affected by the ingredient profile and macronutrient amounts of the bar. 

Cons

• Slower absorption than gels or liquids
• Higher fibre and certain fat content can slow gastric emptying
• More difficult to consume during high-intensity exercise
• Bulkier to carry

Best Applications

• Pre-exercise fuelling (30-60 minutes before start)
• Longer ultra-endurance events
• Training rides/runs at moderate intensity
• Between high-intensity intervals during long training sessions

Chews and Gummies: The Middle Ground

Pros

Carbohydrate chews offer a compromise between gels and bars, providing moderate absorption speed with better palatability over long distances.

Performance Benefits:

• More palatable than gels for some athletes
• Easier portion control
• Moderate absorption speed
• Variety of flavours and textures

Cons

• Slower absorption than gels
• Require chewing, which can be challenging during high-intensity efforts
• May stick to teeth or require more saliva production
• Can be difficult to consume in cold weather

Best Applications

• Training sessions where palatability is important
• Ultra-endurance events where variety prevents flavour fatigue
• Lower-intensity portions of long races
• Athletes who struggle with gel consistency

Real Food Options: The Natural Approach

Pros

Research supports the use of whole food sources, particularly for ultra-endurance events where palatability and nutrient diversity become crucial.

Evidence-Based Options: Studies highlight raisins, bananas, and honey as particularly effective whole food carbohydrate sources due to their portability and rapid absorption characteristics.

Performance Benefits:

• Greater palatability over extended periods
• Provides additional micronutrients
• Psychological satisfaction of "real" food
• Often more cost-effective than commercial products

Cons

• Inconsistent carbohydrate content
• Potential for spoilage or temperature sensitivity
• May contain fibre, fat, or protein that slows absorption
• Less portable than commercial options

Best Applications:

• Ultra-endurance and ironman (bike leg) events (50+ miles)
• Training sessions where practicing race nutrition isn't critical
• Athletes with sensitive stomachs who struggle with commercial products
• Economic considerations for high-volume training

Distance-Specific Recommendations

Short Distance and Training (Under 90 minutes)

For efforts under 90 minutes, endogenous glycogen stores are typically adequate. However, for high-intensity training or when training in a glycogen-depleted state -

• Primary choice: Sports drinks or MARCHON Fuel30 gels
• Rationale: Quick absorption without gastrointestinal burden

Marathon Distance (90 minutes to 4 hours)

This duration requires strategic fuelling to maintain performance while minimising gastrointestinal distress:

• Primary strategy: Combination of gels and sports drinks
• Recommended approach: MARCHON Fuel30 gels every 45-60 minutes with consistent fluid intake
• Backup options: Chews for variety, particularly in the later stages

Ultra-Endurance (4+ hours)

Extended efforts require diverse fuelling strategies to combat flavour fatigue and provide sustained energy:

• Early stages: Bars and real food when intensity is moderate
• Middle stages: Alternating gels, chews, and liquid sources
• Late stages: Whatever is palatable and tolerated
• Key principle: Practice multiple options during training

Gastrointestinal Considerations

Recent research emphasises the importance of gastrointestinal tolerance in fuel selection. Studies comparing different carbohydrate sources show that gels and liquid sources result in less gastrointestinal distress than bars alone. However, individual tolerance varies significantly, making personal experimentation crucial.

Strategies for Optimal Tolerance:

• Start fuelling early in exercise before significant gastric blood flow reduction
• Train the gut with race-day nutrition during long training sessions
• Consider multiple small doses rather than large, infrequent intake
• Maintain adequate fluid intake regardless of carbohydrate source

Practical Implementation Guidelines

Training Phase Integration

Use training sessions to experiment with different fuelling strategies. Long runs and rides provide opportunities to test tolerance and preferences without performance pressure.

Race Day Strategy

Develop a primary fuelling plan with backup options. Weather, intensity, and individual factors can affect tolerance and preference during competition.

Individual Customisation

Consider personal factors including:

• Previous gastrointestinal issues
• Sweat rate and fluid needs
• Exercise intensity and duration
• Environmental conditions
• Practical constraints (aid station availability, carrying capacity)

More information here on how to train your gut.

Conclusion

The optimal carbohydrate source for endurance performance isn't universal—it depends on exercise duration, intensity, individual tolerance, and practical considerations. Research clearly shows that absorption rates and performance outcomes vary between sources, with gels and liquids providing faster energy delivery while bars and real foods offer sustained release and greater satisfaction.

For most endurance athletes, a combined approach works best: using products like MARCHON Fuel30 gels for reliable, rapid energy delivery during critical race phases while incorporating other sources for variety and specific situations. The key is consistent practice during training to identify what works best for your individual physiology and performance goals.

Remember that the best fuelling strategy is the one you can consistently tolerate and implement. Start with evidence-based recommendations, but don't hesitate to adjust based on your personal experience and race-day conditions.