Why Tour de France Fueling Strategies Are Not For You

By Jim Rutberg,
CTS Pro Coach,
co-author of “The Time-Crunched Cyclist”,
“Training Essentials for Ultrarunning”

One of the key storylines from the Tour de France this year (and the past few years) is the extreme carbohydrate intakes in the pro peloton. Elite cyclists and their teams have reported intakes of 100, 120, and even up to 140 grams of carbohydrate PER HOUR. This is a lot higher than the standard recommendations (from ACSM, ISSN, AIS)* to ingest 60-90 grams of carbohydrate per hour during exercise. With the Tour de France and Olympic Games this summer, the ‘extreme carbohydrate intake’ messaging is strong right now. That doesn’t mean super-high carbohydrate is a good idea for you. Here’s why.

Quick “TL;DR” Summary:

• Exogenous carbohydrate intake should be about 40-50% (in kilocalories) of kilojoules of work performed. Pros sometimes do 1000 kilojoules of work per hour, meaning 400-500 Calories of CHO (equal to 100-125 grams) makes sense sometimes.
• Amateur cyclists normally do 400-600 kJ of work per hour, so 40-50% replenishment would equate to 200-300 Calories per hour, or 50-75 grams per hour.
• Overconsumption of CHO when it’s not warranted by energy expenditure increases risk for gastrointestinal distress.

Why Tour de France Riders Eat So Much Carbohydrate

The progression of carbohydrate intake in the pro peloton is kind of a ‘chicken and the egg’ story. For a long time, sports science said the upper limit for carbohydrate absorption in the small intestine was one gram per minute. This led to initial intake recommendations of 40-60 grams of carbohydrate per hour during aerobic exercise.

Subsequent research concluded that mixing carbohydrate sources could increase absorption because individual monosaccharides (simple sugar molecules) used different “gates” or channels to move from the intestine into the bloodstream. The “multiple transporter” research led to mixed carbohydrate sports nutrition products that contain both glucose and fructose, often in a 2:1 ratio. With these products, researchers found athletes could ingest 60-90 grams of total carbohydrate per hour without GI distress.

The next research question was whether consuming even more carbohydrate during exercise would improve performance? In other words, if an athlete could tolerate 100+ grams of carbohydrate per hour, would it make a difference in performance? The answer was yes, but with two important caveats (Podlogar et al, 2022):

1. Energy expenditure needed to be high enough to make use of the additional carbohydrate intake.
2. The ratio of glucose to fructose should shift toward 1:1 or 1:0.8 rather than 2:1.

So, the reason Tour de France cyclists eat so much carbohydrate during (some) stages is because they can. Their energy expenditure during hard stages is high enough (e.g., up to 1000-1200 kJ per hour) to warrant the additional CHO intake, and the new glucose:fructose ratio reduces the risk of GI distress compared to older formulations.

Performance Percentages: How to Fuel Like a Tour de France Cyclist

In principle, you want to fuel like a Tour de France cyclist. The principles are the same, you just want to scale the CHO intake relative to your energy expenditure. During energy-intensity workouts, fast group rides, gran fondos, epic weekend rides, and multi-day cycling tours, aim to consume carbohydrate calories equivalent to 40-50% of your hourly kilojoule output. If you are using a power meter on your bike, your head unit will display kilojoules in real time. You can also review power files in Trainingpeaks, WKO5, or Strava to get an idea of your normal hourly ranges for different types of rides.

For pro cyclists, consuming carbohydrate calories equivalent to 40-50% of 1000 kilojoules per hour of output leads to a recommendation of 400-500 kilocalories of CHO. At 4 kcal/g, that’s 100-125 g/hr. The same math for a fit amateur competitor on a hard day could start with kilojoule output of 600-800 kJ. So, 40-50% replenishment would equate to 300-400 Calories per hour, or 75-100 grams per hour. And, perhaps most important, an amateur during an endurance ride would start with a work output of 400-500 kJ/hr, which would lead to a CHO recommendation of about 50-60 grams per hour (which is exactly where the recommendations have always been!)

Reasons To NOT Consume 100-120 Grams of Carbohydrate Per Hour

Sports science research has shown there’s a dose-response relationship between CHO ingestion and oxidation. In other words, if you consume more CHO you can burn more CHO. And that’s great if you have reason and opportunity to burn that extra carbohydrate. If you don’t, your total energy expenditure stays the same and you burn less fat. At the pro level, the increased carbohydrate intake is advantageous because of the extreme intermittent intensity of bike racing. For amateur racers, events like criteriums, road races, cross-country mountain bike races, and even some gran fondos are short enough that stored glycogen and moderate intakes (e.g., 90 grams or less per hour) are sufficient for optimal performance.

Why not eat more carbohydrate anyway? Well, although there’s a dose-response relationship between CHO ingestion and oxidation, there’s also a dose-response relationship between increased CHO ingestion and GI distress. It takes time for athletes to adjust to consuming and processing 100+ grams of carbohydrate per hour, and even after gut training the risk of GI distress increases with increased hourly food intake.

Gut Training: How To Increase Hourly Carbohydrate Intake

Gut training is the process of gradually increasing the amount of food and fluid your digestive system can tolerate during prolonged exercise. It doesn’t matter whether you’re currently consuming 30 or 90 grams of carbohydrate per hour. Or whether you’re drinking 500 milliliters or 1.5 liters of fluid per hour. Taking your intake up to a new level requires adaptation, which requires time and deliberate practice.

It is best to schedule gut training for a period of generalized training or during an endurance block. You might struggle with nausea or bloating a few times as you push the envelope with food and fluid ingestion. As a result, you want to experience that when the consequences are minimal. You don’t want to jeopardize workout quality during an important block of performance-focused training.

As you work on increasing hourly food and/or fluid intake, experiment with delivery methods. A recent study showed that absorption rates were the same whether cyclists consumed carbohydrates from sports drinks, gels, or chews (Hearris et al, 2022). So, use the form that you enjoy most and the flavors and textures you’re most likely to actually consume. Remember to develop a range of foods and fluids that work for you so you can rotate flavors and textures to avoid ‘palate fatigue’ during long events.

References:

Hearris, Mark A et al. “¹³C-glucose-fructose labeling reveals comparable exogenous CHO oxidation during exercise when consuming 120 g/h in fluid, gel, jelly chew, or coingestion.” Journal of applied physiology (Bethesda, Md. : 1985) vol. 132,6 (2022): 1394-1406. doi:10.1152/japplphysiol.00091.2022

Jeukendrup, Asker. “The Optimal Ratio of Carbohydrates.” Askerjeukendrup, 11 Jan. 2024, www.mysportscience.com/post/the-optimal-ratio-of-carbohydrates.

Jeukendrup, Asker E. “Training the Gut for Athletes.” Sports medicine (Auckland, N.Z.) vol. 47,Suppl 1 (2017): 101-110. doi:10.1007/s40279-017-0690-6

Podlogar, Tim et al. “Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h^-1 versus 90 g h^-1 at different ratios.” European journal of applied physiology vol. 122,11 (2022): 2393-2401. doi:10.1007/s00421-022-05019-w

*ACSM: American College of Sports Medicine; ISSN: International Society for Sports Nutrition; AIS: Australian Institute for Sport