Carbohydrates are the body’s primary source of energy during high intensity exercise. Upon consumption, carbohydrates are broken down to glucose and metabolized for energy. Unused glucose is stored as glycogen in the liver and muscles. After the body has utilized carbohydrate reserves, glycogen is synthesized back into glucose to be used as the alternative source of energy. It is upon this premise that carbo-loading is practiced to improve and sustain athletic performance.
Carbo-loading is the super-compensation of glycogen stores. It is the expectation of carbo-loading that the excess glucose will be converted to glycogen and stored in the liver and muscles. This over abundance of glycogen stores will become the readily available fuel source.
Benefits of Carbo-loading
Because glycogen stores are typically not abundant, energy is often halted upon utilization. Thus, an athlete is said to have “hit the wall”. Carbo-loading maximizes the body’s ability to store glycogen.
Carbo-loading will give an athlete a sustained fuel source over an extended period of time. This alternative fuel source gives athletes energy to compete after their initial glucose reserves are depleted. Endurance athletes utilize this method to perform better during competition. When intense activity extends beyond one and a half to two hours the body is forced to begin synthesizing the glycogen stores for energy. If glycogen stores are insufficient, the body will begin to synthesize amino acids from the muscle tissue. This leads to muscle catabolism, which then leads to a loss of lean body mass.
Another such benefit is believed to enhance the muscularity of bodybuilders during competition. Carbo-loading gives the appearance of bigger, more dense and increased striations of the muscles.
There are two phases of carbo-loading. The depletion stage is where altering the diet soon after high intensity training depletes the glycogen stores. The replenishing stage is where glycogen stores are re-synthesized to above 100% to 150% by consuming an increased amount of carbohydrates.
Glycogen depletion - A few days before you begin glycogen packing, reduce your carbohydrate intake to about 55-60 percent of your total calories. This will prepare your body by depleting existing carbohydrate stores to make room for the excess carbohydrates.
It is recommended that your macronutrient ratio is 60:20:20. Make sure to consume your full caloric intake to avoid muscle loss. Maintain high intensity training until fatigue during this period to ensure depletion occurs.
Glycogen replenishment – Glycogen packing is usually started about three to four days before an event. Increase your carbohydrates to about 70 percent of your total calories.
It is recommended that your macronutrient ratio be about 70:15:15. Another variation of this phase may be 70:20:10, where about 20 percent of your intake is from fat and 10 percent is from protein. However to avoid excess weight gain, it is suggested to limit macronutrient ratios to 15% fat and 15% protein to 70% carbs during the first 24 hours. Reduce training intensity to prevent burning glycogen stores. When carbo-loading, it is important to consume low-glycemic-index foods. This will help to ensure only moderate levels of glucose will be entering the bloodstream over a duration of time. Carbohydrates high on the glycemic index will lead to quick, large amounts of glucose entering the bloodstream causing insulin levels to fluctuate. Maintain water consumption during this phase. Maintain a good source of vitamin and mineral supplements.
If one carbo-loads too often, performance levels can actually be inhibited and if done over an extended duration carb loading can become ineffective. Carbo-loading should be limited to no more than three times a year.
Effectiveness of Carbo-loading
Carbo-loading is found more effective in males than females. There is some speculation that males burn sugar more effectively than do females. Findings indicate that females use fat more effectively than sugars. It is suggested that this may be due to the apparent lower respiratory exchange ratio (RER) of females than males.
Recent findings show no significant improvement when carbo-loading was applied. This is not to suggest that carbo-loading is altogether ineffective, but one should consult a trained professional before determining if this is the preferred method to enhance performance. Many studies also indicate a less than significant improvement in female athletes than male athletes.