Hello my fitness friends! It’s almost game time. Just under 7 days left until the Houston Marathon and Half Marathon. I hope all your training, sweat, and hard work is paying off. And that some of my articles have provided you with some assistance to help you better achieve your goals and prepare you for Sunday's race.

Today, I want to talk about carbohydrate loading and general prep for a race for of this nature. Understanding how to fuel and hydrate your body properly will help you maximize your performance and minimize injury.

Carbohydrate loading, also referred to as “carbo-loading”, is a familiar term among athletes of all abilities levels and sports.

To most runners it is often used to describe a large pasta dinner the night before a race or the consumption of massive amounts of carbohydrate justified by statements such as “I run a lot, so I can eat this.”

It is true that carbohydrate is the body’s major fuel source and is a crucial component of the distance runner’s diet. However, true carbohydrate loading is a systematic and scientific practice that can take the course over the weeks and days leading up to competition with the purpose of maximizing the storage of glycogen (carbohydrates stores) in muscles.

The following is a simplified break down of the who, what, when, why and how of carbohydrate loading and tips for how you can make it work for you.

Who can benefit from carbohydrate loading?

Carbohydrate loading is only effective for endurance events lasting longer than 90 minutes, such as marathons and triathlons.

During intense, continuous endurance exercise, your muscles will become depleted of glycogen after about 90 minutes. Carbohydrate loading is meant to store extra glycogen that your muscles can tap into once the normal stores are used up. Carbohydrate loading is not normally useful for events like a 5k or 10k since the running effort will not be long enough to completely deplete muscle glycogen stores.

What type of carbohydrate loading should you use?

As carbohydrate loading received more attention for its ability to improve athletic performance in endurance events, more research has focused on effective methods.

The traditional method consisted of tapered training accompanied by increased carbohydrate consumption in the weeks leading up to competition. A similar method followed this same model but in a shorter duration of time (6 days). There are also more rapid methods of carbohydrate loading that seek to maximize glycogen stores in the final 24 hours before competition.

The appropriate method for you depends on the event you are doing, your training leading up to the event, and the number of events you plan on doing throughout the year. While some athletes may practice a long taper leading up to a major competition, others prefer to keep a high level of training all the way up to the day of the event. 

Carbo loading method 1: Long Taper

Using the long taper method, you should have your final hard training session 3 weeks before competition day. By 2 weeks out, you should really start tapering your training.

During this taper time you do not need to eat extra calories since your body will not be using as many as it needed during training. Instead, you should continue to eat 3-5 grams of carbohydrate per pound of body weight and reduce your fat intake to make up for your body’s reduced demand for energy.

Your muscles will use these extra carbohydrate calories to build up a glycogen store that will remain, since you won’t be using it for training any longer. Normally your body can store glycogen at the capacity of 80-120 mmol/kg.

Carbo loading method 2: 6-day Protocol

In this method, a glycogen-depleting exercise is performed 6 days prior to the event. This exercise should utilize the same muscle groups that will be used in competition so if you are planning on running a marathon, you would want to do few minutes of very intense sprinting to deplete your muscle glycogen stores.

The next 3 days would consist of a normal mixed diet (~2-3 grams of carbohydrate per pound), and tapered training. Then 3 days before competition you would further reduce training or rest completely and consume a high-carbohydrate (~4.5 grams per pound), low-fat diet.

Carbo loading method 3: Rapid Loading

To do this, the athlete will perform an intense glycogen-depleting exercise 24 hours prior to competition. Immediately following this workout the athlete will start to consume a high-carbohydrate diet consisting of 5-6 grams of carbohydrate per pound and continue this throughout the day.

As an example, an athlete weighing 150 pounds would need to eat about 750 grams (or 3000 calories worth) of carbohydrates. To make room for all of these carbs you would need to greatly reduce your intake of fat and protein for that day.

Final tips for carbohydrate loading

  • First, and foremost, carb loading is not for everyone. I strongly recommend that if you don’t work out and run at least 3-4 days per week and/or you have a sensitive stomach in general and have not incorporated a carb loading method before. Do not carb load.  Especially with the rapid loading method, intestinal problems may occur and you do not want to have to deal with these on race day.
  • Eat an adequate amount of protein (0.6-0.7 grams per pound). Protein may be helpful in assisting glycogen synthesis and can also be used as a secondary fuel source in endurance exercise.
  • Add some fiber-rich foods to promote regular bowel movements but don’t go overboard. Too many refined carbohydrates can result in constipation but too much fiber could cause diarrhea and intestinal distress on race day.
  • Expect a little water weight gain. For every ounce of glycogen the body also stores 3 ounces of water. Although your muscles may feel a little heavier at the beginning of the race these feelings will subside as the body uses up the glycogen and water throughout the race.
  • Use various forms of carbohydrate-dense foods and drinks to meet your needs such as juices, gels, and sports drinks. Be sure to consume whole-grain sources as well to balance out all that sugar. The best carbohydrate sources for loading include: rice, yams/sweet potatoes (white potatoes to a less extent), quinoa, and oatmeal. .
  • Do not wait until your last meal to load up on the carbohydrates. You want to give your body time to digest and a big meal at night may leave you feeling full and uncomfortable in the morning. Instead trying eating your largest meal early in the day prior to competition. 
  • Finally, be sure to still consume some energy sources and fluids during your event. What you have stored up will help you go longer, but it still may not be enough to get you through the entire race without an additional fueling plan.

    I hope that this helps you better prepare your nutritional strategies going into race day.  Now, get to eating and go forth and conquer that Marathon and Half Marathon guys :)


  1. Houmard JA, Costill DL, Mitchell SH, Park RC, Hickner, Roemmich JN. Reduced training maintains performance in distance runners. Intl J Sports Med. 1990;11(1):46-52.
  2. Sherman WM, Costill DL, Fink WJ, Miller JM. The effect of exercise and diet manipulation on muscle glycogen and its subsequent use during performance. Int J Sport Med. 1981;2:114-118.
  3. Fairchild TJ, Fletcher S, Steele P, Goodman C, Dawson B, Fournier PA. Rapid carbohydrate loading after a short bout of near maximal-intensity exercise. Med Sci Sport Exerc. 2002;34:980-986.


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DMP Fitness

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Darryl Perrilloux

Owner/Master Trainer
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