What is Carbo Loading? (2023)

Carbo-loading is a strategy adopted by endurance athletes, to enhance endurance exercise performance by increasing liver and muscle glycogen storage. It’s regularly used in the build-up to important endurance races, principally when race duration is longer than 90minutes.

What does carbo-loading involve?

It involves increasing your daily consumption of carbohydrates in the build-up to long distance races like marathons.

The most common approach is to increase your carbohydrate consumption over the final few days before a big competition. We combine this with a reduction in training volume.

Why is it important?

First, carbohydrate metabolism plays a key role in fuelling endurance exercise performance.

Second, your body only stores enough carbohydrates (muscle and liver glycogen) to sustain approximately 90minutes of exercise.

Third, once your glycogenstores become depleted, endurance exercise performance suffers.

By carbo-loading, we maximise glycogen levels. This helps to delay the point where they become limiting during longer endurance events.

When should you use it?

It’s a useful approach in the build-up to longer endurance events (those lasting more than 90-minutes) including:

  1. Marathons
  2. Ultra running events
  3. Triathlons (Olympic distance or longer)
  4. Duathlons (standard distance or longer)
  5. Cycling events
  6. Cross-country Skiing
  7. Endurance swimming

What about events lasting less than 90 minutes?

If your event lasts less than 90minutes, there’s really not a need to follow a specific carbo-loading strategy.

Instead, focus on reducing training volume (by 25-50%) over the last week before competition. If you do this whilst maintaining your normal intake of carbs, this will naturally lead to increased muscle and live glycogen storage.

Carbo-loading recommendations

Below are some recommendations for events lasting longer than 90minutes.

Endurance events lasting longer than 90minutes

  • Aim to increase carbohydrate intake, by ~100-200g per day, over the final 3-4 days before competition.
  • For most athletes, consuming 8-10g of carbohydrates per kilo of bodyweight is an effective approach to carbo-loading.
  • Ideally, combine this with a 25-50% reduction in training volume over the last week prior to competition.
  • Consume a high carbohydrate meal 3-4hours prior to competition.

Endurance events lasting less than 90 minutes:

  • For races of less than 90 minutes duration, glycogen stores should be more than adequate.
  • Continue with your normal dietary intake of carbohydrate (5-7g of carbs per kilo of bodyweight)
  • Combine this with a 25-50% reduction in training volume over the last week before the race.
  • Consume a carbohydrate based meal ~3-4hours prior to competition.

It’s also worth considering the type of carbohydrates that you are consuming:

(Video) Carb-Loading for Athletes

High vs Low Glycemic Index (GI) Carbs

When carbo-loading, there’s various food options to choose from. One important consideration is the glycemic index (GI). This provides a measure of how rapidly different sugars enter your bloodstream.

The glycemic index allows us to categories foods into low, medium and high-GI foods.

  • High GI foodsare fast releasing — they enter your bloodstream quickly,
  • Medium GI foodsare released more moderately — they enter the bloodstream at a steady rate.
  • Low GI foodsare slow releasing foods — entering the bloodstream more slowly than high or medium-GI foods.

Increasing your consumption of either high, medium, or low GI foods will increase glycogen storage.

So what are the best carbs to use for carbo-loading?… Whilst high, medium and low GI foods all increase glycogen stores; from a health perspective, consuming medium and low GI foods, is the best approach.

Why are low-glycemic foods better?

Low-glycemic foods are more healthy because they do not cause the same spikes in blood glucose and insulin levels.

Benefits of low-GI carbs:

  • Low-glycemic foods do not cause such a large rise in blood glucose levels.
  • They cause less of a spike in insulin levels.
  • Low-glycemic foods are less likely to result in the subsequent drop in blood glucose levels, that often accompanies consuming high-glycemic foods.

Examples of high, medium and low-glycemic foods:

High-glycemic foods (GI score of 70+):white bread, potatoes (boiled, mash), parsnips, white Rice, cornflakes, instant oat porridge, pretzels, watermelon

Medium-glycemic foods (GI score of 56-69):brown rice, basmati rice, baked potatoes, bananas, crisps, couscous, muesli, sweet potato, pineapple, porridge oats (rolled),

Low-glycemic foods (GI score of 1-55):spaghetti (white and wholemeal), long-grain rice, carrots, chickpeas, lentils, kidney beans, milk, apples, pears, cherries, orange, strawberries.

Eating before competition

Why do you need to consume an additional high carb meal just prior to competition?… Essentially, this tops up muscle and liver glycogen stores that start to deplete overnight. It also maintains glycogen levels right up until the start of competition.

How many carbs should you consume?… Research has established that consuming a high carbohydrate meal (3-4g carbohydrate per kg of body mass), ~3-4 hours before exercise, ensures glycogen levels remain full. This enhances exercise performance and time to exhaustion (Wee et al., 2005; Schabort et al., 1999; Chryssanthopoulos and Williams 1997; Sherman et al., 1989; Neufer et al., 1987;).

However, that’s a substantial amount of carbs. And for some athletes, that might be too much (especially if you’re a runner) and may lead to intestinal or digestive problems. My preference is to consume around 2g of carbs per kg bodyweight.

Should you consume low of high-GI foods before competitions?…

Research is not completely clear whether high or low-GI foods are more beneficial (Jamurtas et al., 2011).

Some have suggested that ingesting high-GI foods (3-hours prior to endurance exercise) may be more beneficial for increasing muscle glycogen levels than low-GI food (Wee et al., 2005). However, whilst high-GI foods can improve carbohydrate utilisation, they don’t appear to provide any real benefit over low-GI foods (Febbraio et al., 2000; Jamurtas et al., 2011).

(Video) The Biggest Carb Loading Mistake Cyclists Make

A point to consider here:although high-GI food can enhance carbohydrate utilisation, they can actually negatively affect fat metabolism (Little et al., 2009).

In contrast, low-GI foods appear to have several benefits over high-GI foods:

  • Increased free fatty acid availability,
  • Helps to maintain fat metabolism,
  • Spares muscle glycogen,
  • May reduce muscle lactate levels (Wee et al., 2005).

The benefits of low-GI foods before competition

Some studies have found that low-GI carbs provide greater endurance performance benefits (Moore et al., 2009; DeMarco et al., 1999; Thomas et al., 1991).

When Researchers looked at pre-exercise low and high-GI consumption (30-60minutes prior to exercise); they found that low-GI carbs had the following benefits:

  • Greater increases in time to exhaustion (Thomas et al., 1991),
  • Increased time to exhaustion following a 2-hr submaximal cycle (DeMarco et al., 1999)
  • Improved 40km time trial performance (Moore et al., 2009).

Although, it is not altogether clear whether low or high-GI foods are better prior to exercise; research is more supportive regarding low-glycemic carbs (Moore et al., 2009; Wee et al., 2005; Siu and Wong, 2004; DeMarco et al., 1999; Thomas et al., 1991).

Why high-GI foods may be negative before exercise:

This is mainly because High GI foods cause a rapid spike in blood sugar and insulin levels.This has two negative effects that may compromise endurance exercise performance:

First, when insulin levels rise too rapidly, they overcompensate for the actual amount of sugar in the blood. This can lead to a state of low blood sugar (hypoglycaemia).

Second, high insulin levels have an inhibitory effect on the mobilisation and use of fat as an energy source.

The combination of inhibited fat metabolism, and reduced blood sugar levels, can increase depletion of glycogen stores. Why is that?… This is due to increased reliance on glycogen stores; because of a need to compensate for the lower blood sugar levels and reduced levels of fat metabolism.

If you start your race in this state, then carbohydrate metabolism will have to increase, leading to increased glycogen depletion.

With this in mind, it makes sense to favour low-glycemic carbs, both during the initial carbo-loading phase and for the final pre-race meal.

Keeping hydrated is essential

While carbo-loading, it’s important to ensure that you maintain an adequate intake of fluids. This is important because the storage of glycogen also requires additional fluid storage. In fact, your body stores ~3g of water for every gram of glycogen.


  • Carbo-loading is a strategy used to increasing muscle and liver glycogen levels.
  • It’s most effective when used for events lasting more than 90minutes.
  • It involves increased carbohydrate consumption – typically for 3-4 days just prior to competition.
  • For shorter duration races (less than 90 minutes), carbo loading may not be necessary. Instead, reducing your training volume will help to maximise glycogen levels.
  • Carbo-loading can be combined with a 25-50% reduction in training volume. This helps to enhance recovery and aids muscle glycogen storage.
  • Consuming an additional high carbohydrate meal (3-4 hours before competition), can enhance endurance exercise performance and time to exhaustion.
  • Low-GI foods are considered more beneficial for carbo-loading. Andappear to aid fat metabolism and for maintaining muscle glycogen levels.
  • Consuming a meal that is too High GI, may negatively affect endurance performance by increasing insulin levels. This can lead to a spike in insulin, lower blood glucose levels, and may inhibit fat metabolism.
  • Hydration levels need to be sufficient throughout the carbo-loading phase.


Acevado, E.O. and Goldfarb, A.H. (1989). Increased training intensity effects on plasma lactate, ventilatory thresholds, and endurance. Medicine and Science in Sports and Exercise. 21, 563-568.

(Video) How to CARB LOAD Before a Race | Marathon Prep, E15

Costill, D.L. (1986). Inside Running: Basics of Sports Physiology. Benchmark Press: Indinapolis, USA.

Coyle, E.F., Feltner, M.E., Kautz, S., Hamilton, M.T., Montain, S.J., Baylor, A.M., Abraham, L.D. and Petrek, G.W. (1991). Physiological and biochemical factors associated with elite endurance cycling performance. Medicine and Science in Sports and Exercise. 23, 93-107.

Fallowfield, J.L. and Wilkinson, J.L. (1999). Improving sports performance in Middle and Long-Distance Running. Chichester: John Wiley and Sons, LTD.

Jones, A.M. (1998). A five year physiological case study of an Olympic runner. British Journal of Sports Medicine. 32, 39-43.

Londeree, B.R. (1997). Effect of training on lactate/ventilatory thresholds: a meta analysis. Medicine and Science in Sports and Exercise. 29, 837-843.

Martin, D.E. and Coe, P.N. (1997). Better Training for Distance Runners (2nd edition). Human Kinetics: Champaign, IL, USA.

Neumann, G., Pfutzner, A. and Berbalk, A. (2000). Successful Endurance Training. Oxford: Meyer and Meyer Sport (UK), LTD.

Noakes, T.D. (1991). Lore of Running. Human Kinetics: Champaign, IL, USA.

Pate, R.R. and Branch, J.D. (1992). Training for endurance sport. Medicine and Science in Sports and Exercise. 24, S340-343.

  • Endurance Nutrition Basics
  • Carbohydrates during exercise
  • Carbs after exercise
  • Fat intake for endurance athletes
  • Why endurance runners should practice race day nutrition


What is carbo loading? ›

Carbohydrate loading occurs when you eat a high-carbohydrate "training diet" at the same time that you scale back your activity level in the days before an event.

What is good carbo load? ›

Dairy products such as almond milk, rice milk, Greek yogurt and cottage cheese provide a healthy dose of carbohydrates while also containing a high level of protein. But don't make yogurt the go-to pre-run snack, as it takes over two hours for the body to fully digest.

What is an example of carb-loading? ›

For example, if you weigh 154 pounds (70 kg) and you normally eat 300 grams of carbs per day, then you are consuming 1.9 grams per pound (4.2 grams per kg) of carbs per day. People who are carb loading may eat 2.3–5.5 grams of carbs per pound (5–12 grams per kg) of body weight per day.

What is carbo loading quizlet? ›

Carbohydrate loading is described as. depleting glycogen stores by intense intense exercise along with little carbohydrates and then less exercise and a higher intake of carbohydrates to increase glycogen storage.

Who invented carbo-loading? ›

The practice of carbo-loading dates back to the late 1960s. The first carbo-loading protocol was developed by a Swedish physiologist named Gunvar Ahlborg after he discovered a positive relationship between the amount of glycogen (carbs stored in the muscles and liver) in the body and endurance performance.

How does carbohydrate loading improve performance? ›

Carbohydrate loading increases muscle glycogen stores, giving individuals more energy at their disposal to use during exercise. Eating sufficient carbohydrates also helps to build muscle mass and prevent muscle loss.

How do you carbo load before a race? ›

The morning of the race: 1.5-2.5 g of carbs for every 1 kg of body weight 3-4 hours before the race and a smaller carbohydrate snack -banana, bar, bread, 1 hour before the race. Also, have in 5-7 mL of water/electrolytes fluid per 1kg of body weight.

Do you carb load the day before? ›

To carb-load properly for the race, you will be tapering in the days and weeks beforehand. If you want to experiment in advance, you can carb-load the day before a long run, but it won't quite be the same since you'll only be fueling 24 hours out, and you won't have the benefit of rest and taper.

How long should you carb load before a race? ›

Experts advise starting serious carbo-loading 3-7 days before the race. At this point, 85 to 95 percent of your calories should come from carbohydrates. During these last few days you'll also want to cut back your running to allow glycogen to accumulate.

Is carb-loading good for weight loss? ›

Research shows that carb loading can temporarily raise metabolism and increase levels of leptin, a hormone that blunts hunger, which, together, could help promote weight loss.

What do I eat the night before a marathon? ›

Choose refined carbohydrates, like white rice, pasta and bread, and avoid high-fibre foods like whole grains, beans and legumes. Eat a high-carbohydrate bedtime snack, like a small bowl of oatmeal or granola.

Is Pizza Good for carb-loading? ›

“Pizza has a very high carbohydrate content, so if you're carb-loading before an event it can be included in your diet – in moderation of course,” says Reid. However, unless you're purposefully upping your carb content go for a thin base and don't add extra cheese because this will up the fat content considerably.

What is the advantage of carbohydrate loading quizlet? ›

The major advantage of carbohydrate loading is the increased storage of glycogen in the adipose cells for use during exercise.

Why does carbohydrate loading increase the performance of athletes quizlet? ›

Carbohydrate loading is an evidence-based technique that can be beneficial for endurance athletes by delaying fatigue, enhancing endurance performance, and maximizing muscle glycogen stores. However, weight gain is a common outcome because the glycogen is stored with water.

What are the advantages of carbohydrate loading for an endurance athlete quizlet? ›

Why would carbohydrate loading be beneficial? By altering their diet and exercise, a person can increase their glycogen stores by 50-85%, which means that they are able to compete longer (especially those activities, such as marathons, triathlons or soccer.)

Is carb-loading good for weight loss? ›

Research shows that carb loading can temporarily raise metabolism and increase levels of leptin, a hormone that blunts hunger, which, together, could help promote weight loss.

How do athletes carbo load? ›

Carbohydrate loading, also known as carb-loading or carbo-loading, is when athletes consume a large amount of carbohydrates before a major athletic event. Carb-loading is helpful for athletic events that call for long endurance or short-term, intense exercise activities.

Should I carb load the night before? ›

According to Mayo Clinic, carb-loading should start one to three days before your athletic event. So, that time period can include the night before a workout — if your training will last 90-plus minutes.

Is it good to carb load before a workout? ›

A good rule of thumb, Sklaver says, is to eat 25 percent of your daily carbohydrate allotment 1 to 4 hours before a workout and another 25 percent within 45 minutes of finishing your workout. The remaining 50 percent of your carbohydrates should be evenly distributed throughout the day.


1. Carb Loading: How to Properly Fuel for Your Next Event (Ask a Cycling Coach 244)
2. Michael Carbo Loading - The Office US
(The Office)
3. Carboloading I Ernährung vor einem Marathon I Laufbegriffe kurz erklärt
4. Glycogen / Carbo-loading
(James Morris)
5. Carbo Loading: Explained the correct way by Sports Dietitian
(Coach Jeaneth Aro)
6. How to Carb load for Runners
Top Articles
Latest Posts
Article information

Author: Trent Wehner

Last Updated: 22/05/2023

Views: 5951

Rating: 4.6 / 5 (76 voted)

Reviews: 91% of readers found this page helpful

Author information

Name: Trent Wehner

Birthday: 1993-03-14

Address: 872 Kevin Squares, New Codyville, AK 01785-0416

Phone: +18698800304764

Job: Senior Farming Developer

Hobby: Paintball, Calligraphy, Hunting, Flying disc, Lapidary, Rafting, Inline skating

Introduction: My name is Trent Wehner, I am a talented, brainy, zealous, light, funny, gleaming, attractive person who loves writing and wants to share my knowledge and understanding with you.