When engaging in high-intensity endurance exercises, carbohydrates serve as the primary fuel source for your body. A critical question arises: how much carbohydrate should you consume to maximize your performance? Determining the appropriate carbohydrate intake is fundamental to crafting an effective fueling strategy for races and essential training sessions. Despite its significance, many athletes lack a clear understanding of their ideal carb consumption.
Prioritizing Your Needs
The confusion surrounding optimal carbohydrate intake for athletes stems partly from decades of sports nutrition marketing that have inadvertently obscured our priorities. Brands often emphasize the source of carbohydrates in their products rather than the quantity needed or the suitability of the product format (e.g., gel or drink) for individual needs. The market is saturated with hype around innovative formulations and carbohydrate sources, such as ‘Hydrogel Technology,’ ‘Cluster Dextrin™,’ and ‘SuperStarch’.
This focus on the source, rather than the amount, is a marketing tactic to differentiate similar products in a competitive market. Discussions about determining the precise grams of carbohydrates needed for optimal performance are less frequent, even though this is arguably more crucial. Generic advice like “Take one to three servings per hour during exercise, less if you’re also using a sports drink” is often the extent of guidance provided.
Considering Maslow’s Hierarchy of Needs offers a helpful perspective. Maslow’s model places basic needs (food, water, and warmth) at the base of a pyramid. Only when these fundamental needs are met can we effectively address higher-level needs like safety, belonging, love, self-esteem, and self-actualization.
Fueling can be viewed similarly:
The source of carbs in energy products isn’t entirely irrelevant, but it’s less important than consuming the right amount of calories in a format that’s logistically practical for your specific sport.
The Role of Carbs During Prolonged, Intense Exercise
Glycogen is the primary carbohydrate source that fuels your body during the initial stages of exercise. Glycogen, composed of chains of glucose molecules, is stored in the muscles and liver. Consider it your checking account for energy, while fat is like your long-term savings.
However, glycogen stores are finite. Roughly 90-120 minutes of intense activity can deplete these stores, significantly impairing performance.
Therefore, ingesting carbohydrates (through drinks, gels, bars, or carb-rich foods) becomes essential for maintaining a high level of output over extended periods. Relying solely on fat for fuel does not support the intensity required for competitive racing.
Carbohydrates consumed during exercise are known as ‘exogenous’ fuel—extra ‘cash in your hand’ while you’re exercising.
Due to the performance-enhancing potential of exogenous fuel, the optimal amount and type of carbohydrate to consume have been extensively researched for over 50 years. Consequently, clear, tested guidelines exist for determining the necessary carb intake to optimize performance across various durations and intensities of exercise.
Hourly Carbohydrate Requirements
When considering carb intake recommendations, two essential assumptions apply:
- You start exercise with adequate glycogen stores. Consume a light, carb-dense meal or snack 2-3 hours before exercising. If glycogen stores are low, carbohydrate requirements during exercise may be higher (if tolerable).
- The goal is optimizing performance, not merely completing the activity. This implies pushing yourself intensely, as you would in a competitive setting.
These guidelines do not apply to easy 2-hour training rides or runs at a steady pace. At lower intensities, the body utilizes more fat, thus reducing the need for exogenous carbs.
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Now, let’s explore the basic recommendations.
Carbohydrate Intake Per Hour: A Visual Guide
Note: When consuming over 60 grams of carbohydrate per hour, a 2:1 glucose/fructose mixture can be advantageous.
Exercise Under 1 Hour
Athletes with sufficient glycogen stores generally do not need to consume carbohydrates during activities lasting less than an hour.
Replenishing glycogen stores with a carb-rich recovery meal or snack after exercise is sufficient, especially if you plan to train or compete again shortly. However, consider the duration and intensity.
For extremely short durations (<30 minutes), carbohydrate ingestion shows minimal impact on performance.
However, for slightly longer durations (45-60 minutes) at “all-out” intensity, evidence suggests that performance may benefit from a small amount of carbohydrate ingestion or a carbohydrate mouth rinse, which is convenient during intense racing when swallowing is difficult.
A carbohydrate-rich drink is ideal for such efforts because it’s easier to consume (or ‘swish and spit’) than gels, energy bars, or even pizza.
Exercise Lasting 1-2 Hours
As duration increases, so does the potential benefit of exogenous fueling. In this timeframe, carbohydrate ingestion will significantly improve your performance.
For durations between 1-2 hours, consuming approximately 30-60 grams of simple carbs per hour is beneficial. This equals roughly 500ml-1l (16-32oz) of a standard isotonic (~6% carb) energy drink or 1-2 standard energy gels per hour.
The harder the effort and the longer the duration, the more appropriate it is to increase intake to around 60 grams per hour, particularly for highly fit athletes who can sustain high workloads.
Beyond two hours, research generally supports a dose-response relationship, with higher carb intakes correlating with better performance outcomes.
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Exercise Over 2 Hours
Athletes exceeding the 2-hour mark benefit from higher intakes of 60 to 90 grams of carbohydrate per hour, provided it doesn’t cause stomach issues. Consequently, faster competitors in long races often have the highest carbohydrate intake rates.
The high carb intake levels reported by Tour De France riders and IRONMAN winners highlight that racing long distances at a fast pace is as much an eating event as an athletic one!
The higher the intended carbohydrate intake, the more crucial it is to practice and ‘train your gut’.
Consuming ~90 grams per hour (e.g., 3 x PF 30 Gels or 3 x PF 30 Energy Chews or 1 x PF 90 Gel) is not immediately achievable for all athletes and may require time to build up, especially for those prone to gastrointestinal issues.
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At this level of carb consumption, the source of carbohydrates becomes more important. ‘Multiple transportable carbohydrates’ (MTCs) such as Glucose/Fructose blends can maximize carb absorption. MTCs are different types of sugar.
While ~90g/hr was once considered a firm ceiling for carb intake, anecdotal evidence suggests some athletes consume even more. Even approaching 90g/hr is impressive for most, but a movement exists in elite sports for even higher doses.
For ‘ultra’ exercise (often defined as 6+ hours), other fueling considerations arise beyond a simple ‘carbs per hour’ approach. These include the benefits of fat and protein from ‘real foods’ and issues with taste fatigue. A full discussion of fueling for ultras is beyond this article’s scope.
The key takeaway is the 30 to 60 to 90g per hour concept, with carb doses increasing significantly as exercise duration increases.
Most amateur athletes tend to under-consume carbs during hard training sessions and races. If these numbers seem high compared to your current intake, it signifies potential for improvement by increasing your fuel consumption.
Training your gut to absorb intakes above ~60g per hour may be necessary for optimizing performance in long, hard events. Don’t be discouraged by initial gastrointestinal discomfort.
This area is where research is catching up with elite athletes. If seeking to increase carb intake, gradually increasing consumption from your current tolerable limit during one or two hard sessions per week over 4-6 weeks is the recommended approach.
Know Your Numbers
The Fuel & Hydration Planner helps athletes determine their needs. Use the calculator to estimate your hourly carbohydrate needs based on activity intensity and duration.
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Our PF 30 Gel, PF 90 Gel, PF 300 Flow Gel, PF 30 Chews, Carb & Electrolyte Drink Mix and Carb Only Drink Mix clearly state the carb content per serving on the packaging, making it easier to achieve your targets during exercise.
The Influence of Body Size on Carbohydrate Intake
One might assume larger athletes need more carbs to fuel higher energy outputs. However, recommended carbohydrate intakes are in grams per hour, not grams per kilogram of bodyweight per hour.
Body mass is not a highly relevant factor because the rate at which sugars are absorbed in the gut is similar for all athletes, regardless of body size.
The advice is essentially the same for a 50kg (110lbs) athlete and a 90kg (198lbs) athlete because the limiting factor is the amount of carbohydrate that can move through the gut into the bloodstream per minute.
Evidence suggests that smaller athletes may benefit more from higher carb doses because the relative contribution of exogenous carbohydrate oxidation to total energy expenditure is greater for them.
Studies in this area have typically used athletes with limited body size ranges. At the extremes, there may be some differences in carbohydrate absorption rates.
There’s also natural variation between athletes due to individual gut microbiomes. However, body size is a less influential factor in setting carb intake rates than common sense suggests.
Image Credit: Dale Travers ©
Visualizing 30, 60, and 90g of Carbs Per Hour
How an athlete chooses to ingest their carbs varies individually. Options include sports fuels like gels, chews, bars, Energy Drink Mix, and real foods.
The pros and cons of each warrant a separate discussion, but as long as it ‘agrees’ with your digestive system and works practically within your sport’s constraints, there are few ‘right’ or ‘wrong’ answers.
The key is delivering the correct amount of carbohydrate per hour to meet your energy needs.
Here’s a table showing the typical carb content in common energy products:
| Food / sports nutrition product | Carbohydrate content |
|---|---|
| Sports energy gel* | Usually 20-30g (variable) |
| PF 30 Gel | 30g |
| PF 90 Gel | 90g |
| PF Carb & Electrolyte Drink Mix | 60g per litre |
| PF 30 Chews | 30g (2 x 15g chews) |
| Sports chews* (per serving, can be ~4 chews) | 20-30g (variable) |
| Typical energy bar | 40-60g |
| Medium banana | ~25g |
| Jelly babies (per 4 sweets) | 21g |
| Coca Cola (375ml can) | 40g |
*Always check the packaging on products as different brands contain different types and amounts of carbohydrates.
Now that I know my numbers, what’s next?
Now that you better understand your carbohydrate needs, consider what types of products or foods are best for you.
This varies significantly from sport to sport and depends on exercise duration, intensity, environment, and personal preferences.
