Glycemic Index for Athletes
Glycemic Index in Athletes and Weight management
by Mike Nystrom
The glycemic index of carbohydrates pertains directly to athletes and their performance. The glycemic index of a carbohydrate can be summed up very simply by saying that the higher the index of the food the faster it will be absorbed in the body and blood, therefore, the faster it will raise blood sugar levels. This can have both positive and negative effects on the human body.
Most knowledgeable nutritionists maintain that the American diet should consist of a balance three macronutrients (carbohydrates, protein, and fats). “Currently, the majority of our nation's health experts support a plant-based diet which is high in carbohydrate (45 — 65% of total calories), moderate in fat (20 — 35% of total calories) and adequate in protein (10 — 35% of total calories) .” (Wein, 2007) The critical attribute to this diet is what type of carbs the carbohydrate portion includes. The type of carbohydrate is determined by many different factors, “The digestibility of the starch in the food.
- Interactions of the starch with the protein in the food.
- The amounts and kinds of fat, sugar, and fiber in the food.
- The presence of other constituents, such as molecules that bind starch.
- The form of the food (dry, paste, or liquid; coarsely or finely ground; how thoroughly cooked; and so forth).
- The combination of foods consumed at a given time.” (Wein, 2007)
Based on these different attributes the foods are classified as either low, medium, or high on a glycemic index scale. Typically high G.I. foods, or what I call fast carbs, are absorbed and raise blood sugar very quickly while lower glycemic foods, slow carbs, do the opposite. “Foods can be classified by their glycemic index (GI) as either low, medium, or high (See table 1). High GI foods are absorbed quickly by the gut and rapidly raise blood sugar levels, whereas low GI foods are absorbed slowly and have a moderate effect on raising blood sugar levels.” (Wein, 2007)
Foods high in G.I value are typically those that are high in simple sugars. Many cold cereals, cola's, refined breads, and foods that are highly processed and preserved will have a high glycemic value. These foods are excellent to be used after intense exercise to jump start the recovery process, while being used before can cause a rapid drop off in blood glucose levels that I will discuss more later on. Whole grains, brans, and oats are excellent sources of fiber and mid range glycemic carbs which are best for an athlete to ingest before exercise as effects will be long lasting. The lower end of the glycemic index is made up of primarily legumes, beans, and green leafy vegetables.
"High GI Foods" - "Low-Medium GI Foods"
Foods of all different glycemic values have their places at different times. Athletes should consider these points to help their performance. “Research suggests that endurance athletes may benefit from eating low-GI foods before exercise because these foods release glucose slowly into the bloodstream, which can help to sustain blood glucose levels.” (Wein, 2007) Any athlete or avid exerciser should consider this advice. “During prolonged exercise, consuming foods or fluids with a medium or high GI may promote carbohydrate usage and therefore help to maintain adequate blood glucose levels.” (Wein, 2007) This is great advice for those who exercise for long periods of time, like cross country athletes and marathoners. “After exercise, athletes should try to consume foods and / or fluids with a high GI in order to promote rapid glycogen repletion.” (Wein, 2007) This point is most valuable to weightlifters and has been around a very long time. The most effective post workout creatine supplements embrace this idea by fueling uptake of their product via high levels of simple sugar. This aids the creatine in getting into the cell, and helps to refuel glycogen stores immediately and being muscle recovery.
I am very familiar with most of these concepts and believe strongly in them. The glycemic index is a very valuable tool, especially in the area of weight loss. At times of the year when I diet extensively I employ many of these ideas. Using higher glycemic foods early in the day can lead to crashing, and any crashing leads to large swings in blood sugar levels. Crashing can also be extremely detrimental before an athletic event or training session. If you have ingested a food extremely high in glycemic index and load the drop off will be severe; I would compare it closely with the adrenaline loss in the early stages of a football game. As many players know when that adrenaline leaves the energy loss is so intense that it can take your breath away, but you can recover in the midst of action. In this case your loss of energy will hang around until more glucose is mixed into your blood.
Large changes in blood sugar levels also create an environment in which fat stores are readily held; the precise thing most dieters want to avoid. As for some routine principles to maintain weight, never spiking the blood sugar except for immediately after exercise is a good one to follow. The faster glycogen stores can be replenished the faster recovery can take place. Recovery is critical for strength gains, and full glycogen stores will contribute to protein synthesis; an essential element for muscle repair.
Also, if your body becomes accustomed to regulated levels, they will be less likely to ever swing dramatically. The diet should be made of foods that come from the moderate glycemic side earlier in the day and should be tapered in value as the day goes on. As bed time approaches only foods very low in glycemic value should be eaten. Carbs are an excellent source of energy and should not be avoided. They should be ingested in a controlled manner, with simple sugars being kept to a minimum. The RDA recommends 10% of carb intake from simple sugars, in my estimations dieters would want to cut that to as low as 3-5%. Again, the glycemic index is an extremely useful tool in increasing athletic performance and in controlling and losing weight.
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Source References
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- Wein, Debra. Glycemic Index for Athletes. NSCA's Performace Training Journal: A Free Publication of the NSCA. 2004. Retrieved 06, 03, 2007.
