Carb-loading – Done Properly

Glycogen super-compensation, also known as “carb-loading,” is a term often thrown out as an excuse for every athlete to indulge in heavy iman with his face in a plate of pastantake of starch based foods. Technically, true carbohydrate loading may require heavy intake of starch based or other carbohydrate rich foods. But, not all athletes benefit from loading up on large quantities of carbohydrate. Carb-loading done properly can offer performance benefits for athletes who do 90 minutes or more of continuous cardiovascular exercise in endurance athletes. While indulging in lots of carbohydrates may sound appealing to some, most endurance athletes struggle to ingest the necessary amount of carbohydrates for proper carb-loading, especially because it must be done at a time when they are less active.

Carb-loading benefits endurance athletic performance by postponing fatigue during exercise. It won’t help you go faster, but it may allow you to maintain your desired pace longer, 20% longer in fact. Carb- loading also can improve performance over a set distance or workload by 2-3%2. These benefits are directly related to the fact that by carb-loading, your body has more fuel on board. Normally, the body stores about 2% of its energy sources in the form of glycogen (~92% fuel stored as fat). By carb-loading properly, you can increase your body’s storage of glycogen by 50-80%, or more3. Extra fuel means you can go extra far with less fatigue.

There are three basic carb-loading models: 1.) the Classic week long strategy, 2.) the Moderate carb- loading model, and 3.) the Rapid carb-loading plan2. There are pros and cons to each model, but each can successful be used to increase the amount of glycogen stored in your body above and beyond its normal capacity. See the chart below for details.

Special mention should be given to females when it comes to carbohydrate loading. Typically females are less, or not successful at all, with achieving glycogen super-compensation. This seems to be mostly related to the lower energy intake of females. Compared to men, even when equal percent increases in dietary carbohydrate are supplied, women do not achieve increased glycogen storage, while men easily do4. Women typically must greatly exceed their daily calorie requirements to achieve the necessary amount of carbohydrate needed per pound of body weight to successful carb-load. It seems that if a female is on her period, she may have even more difficulty taking in adequate carbohydrate5. However, females are fully capable of achieving glycogen super-compensation and the associated benefits. But it may present more of a challenge compared to men.

Lastly, it should be noted that every extra gram of glycogen stored in the body brings with it 3-5g. of water. This may result in a 2-3% increase in body mass during the carb-loading process2. Most athletes

find this uncomfortable and report feeling, “bloated.” This feeling is likely enhanced by their taper of exercise that is also required during this time. The positive is that the excess water retained will quickly be used, along with the glycogen, during competition. Emphasis should be given to increase fluid intake, along with carbohydrate intake, in the days leading up to competition.

 

Classic Carb Loading

6-7 days total

  • First 3-4 days
  • Carbohydrate depleting days: 0.5g. carbohydrate per pound body weight or ~<10% of total calorie intake
  • Last 3-4 days
  • exercise taper and carbohydrate loading days: 3.7-4.6 g. carbohydrate per pound body weight, or lean mass- which is~ 78-90% of total calorie intake
  • Moving from depletion phase to loading phase may cause great GI-upset

Moderate Carb-Loading

  • 3-4 days total
  • No true depletion phase (or 3 days prior to carb-loading days, regular strenuous exercise, which is defined as <70% VO2max or 7 on the rate of perceived exertion scale of 1-10 and at least for 40 or more in duration, but carbohydrate intake remains average.)
  • First 2-3 days carb-loading
  • Pair 3.7-5.5g. carbohydrate per pound of body weight, or lean mass with 20 minutes or
  • less easy training
  • Last Day of carb-loading
  • Carb-loading continues with 3.7-5.5g. carbohydrate per pound of body weight, or lean mass, but all training comes to a rest.
  • Glycogen stores will be almost as high as what can be achieved with the classic loading model

 

Rapid Carb-Loading

  • 24 hours total
  • 3.7-5.5g. mostly high glycemic carbohydrate per pound of body weight, or lean mass paired with rest
  • Only works for well trained athletes

 

References:

  1. 1.)  Sedlock DA. The Latest on Carbohydrate Loading: A Practical Approach. Current Sports Medicine Reports. July/Aug. 2008. 7(4):209-213.
  2. 2.)  Jeukendrup AE. High-Carbohydrate Versus High-Fat Diets in Endurance Sports. Schweiz. Ztschr. Sportmed. Sporttraum. 2003. 51:17-23
  3. 3.)  Metzger J. Carbohydrate Super-compensation: Fact or Fiction? Understanding the Truth Behind ‘Carb-Loading’. Journal of Science in Sport.
  4. 4.)  Tarnopolsky MA, Zawada C, Richmond LB, et al. Gender Differences in Carbohydrate Loading are Related to Energy Intake. Journal of Applied Physiology. July 2001. 91(1): 255-230.
  5. 5.)  McLay RT, Thomson CD, Williams SM, Rehrer NJ. Carbohydrate Loading and Female Athletes: Effect of Menstrual-Cycle Phase. International Journal of Sport Nutrition and Exercise Metabolism. 2007. 1792): 189-205.
  6. 6.)  Burke LM. Nutrition Strategies for the Marathon: Fuel for Training and Racing. Jan.2007. Sports Medicine. 37(4-5):344-347.
  7. 7.)  Bussau VA, Fairchild, TJ, Rao A, et al. Carbohydrate Loading in Human Muscle: An Improved 1 Day Protocol. European Journal of Applied Physiology. 2002. 87(3): 290-295.

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About Mari-Etta Parrish

MariEtta Parrish is Registered Dietitian who owns her own Nutrition Consulting company in Nashville, TN, called Healthlete. She is one of only four Dietitians in the state of Tennessee that have a board specialty in Sports Nutrition. She works with individuals, companies, and teams to help them achieve their goals using focus, food, and fitness. Currently she is the Team Dietitian for the Tennessee Titans and the Nashville Predators, but devotes as much passion to the local weekend warriors and to mentoring students. Most importantly, she “practices what she preaches.”
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