understanding the Importance of Glycemic Response and Insulin

Changing the Face of Sports Nutrition
Understanding Low Glycemic Index / Glycemic Response
By Terry Giles

Athletes don’t follow low carb and no carb diets for good reason – carbohydrates fuel their training and the athletes are dependant on carbs for energy and stamina. Athletes have a better understanding on how to balance their diets and nutritional intake by consuming the right mix of carbohydrate sources (starchy and fibrous) and consuming the right amount of carbohydrates (grams per day) depending on their particular needs and training schedule. I have trained hundreds of professional and top amateur athletes to championship titles understanding and utilizing proper nutrition and a complete understanding and study of carbohydrates and their effects on performance. I prefer to stagger carbohydrate intake, both in the amount (grams) per day (consumed) as well as the particular sources. That is another article I will share with you all later, my purpose in this article is to give you an insight and hopefully a better understanding of the impact carbohydrates have in your diet as well as your performance, based on understanding the effects of the glycemic index and the glycemic response of the foods (carbohydrates) you are consuming.

The amount of carbohydrates required for you to consume per day is dependant on the degree of muscle and liver glycogen depletion, and this depends upon your metabolic rate and the duration and intensity of your training. Optimal carbohydrate consumption is dependant on your body’s efficiency to metabolize the carbohydrates you are consuming and the efficiency in which the glucose from these carbs is turned into glycogen and utilized. How carbohydrates affect the metabolism and how they are utilized is dependant on how fast glucose from the carbs you eat enters the bloodstream (how fast it is absorbed from the gastrointestinal tract) and how fast it is removed (how fast it is absorbed from the blood stream into the tissues).

Factors like glycemic response (based on glycemic indexes) and insulin response, all directly affect your body’s ability to utilize the carbohydrates you are eating. For many years people thought that by simply choosing foods with a Low Glycemic Index to consume, it would insure them of a Low Glycemic Response. Unfortunately that simply is not the case. A lot depends on the combination of foods you are eating. A given food is assigned a particular GI (glycemic index) number based on that food’s postprandial (after ingestion) insulinemic response (related to mean glucose and insulin responses as well as blood glucose levels). Look at it this way; glycemic indexing is a system of classification in which the glycemic responses of foods are indexed against a standard (white bread) with the calculation of glycemic response being the most important. This is were fats, proteins and mixing different carbohydrates sources as well as how they are cooked come into play. All of these variables have an effect on the glycemic response of the foods no matter what their glycemic index because they alter the foods absorption in the gut and the clearing out of the bloodstream. That is what makes nutritional supplements so important in relation to the glycemic index and glycemic response tables.

Nutritional supplements, like protein powders or protein bars are most often consumed with no other food source, they are eaten by themselves and have no other foods interfering with their glycemic profile or digestion and clearing. These supplements are designed and formulated in a specific manner so they are low glycemic and their response in the body (glycemic response) will be known. Not all protein powders are low glycemic just because they are low in carbohydrates. It all depends on the exact ingredients and their interactions with each other. It is not just based on calculations, but hard scientific study and testing. I have been fortunate to be involved in the development and advancements being made in nutritional technology and the understanding of the impact nutrition has on athletic performance as well as general good health.

To better understand the role and importance of Low Glycemic Index (LGI) and Low Glycemic Response (LGR) we must first understand the impact of insulin and blood glucose levels on muscle growth, endurance, performance and fat storage. The human hormone insulin is a small protein with a molecular weight of 5808 composed of two amino acid chains connected to each other by disulfide linkages as shown below:

NH2 S S NH2 NH2 NH2

Gly–Ileu -Val–Glu–Glu–Cy–Cy–Thr–Ser–Ileu–Cy–Ser–Leu–Tyr–Glu– Leu-Glu-Asp-Tyr-Cy-Asp

S S

NH2 NH2 S S

Phe-Val-Asp-Glu-His-Leu-Cy-Gly-Ser-His-Leu-Val-Glu-Ala-Leu-Tyr-Leu-Val-Cy-Gly-Glu-Arg-Gly-Phe-Phe-Tyr-THr-Pro-Lys-Thr

A Basic Understanding of Insulin
Insulin has a direct effect on the metabolism of protein, carbohydrates and fat. Insulin has been more closely associated with blood sugar levels, due to its profound effects on carbohydrate metabolism, however, we want to understand as much as possible on insulin’s affect on protein metabolism and fat metabolism as well. All to achieve a better understanding of harnessing insulin’s anabolic actions and maximizing its effects on muscle synthesis, protein utilization and body fat stores in our bodies. Insulin secretion is related to energy abundance. When there is an abundance of energy producing foods in the diet, as in the forms of carbohydrates and proteins, insulin is secreted in large quantities; this is especially true for excess carbohydrates and less for excess proteins. Insulin also plays a vital role in the storage of these excess energy nutrients. Excess carbohydrates are stored as glycogen mainly in the liver and the muscles, and as all of these excess carbohydrates cannot be stored as glycogen, the remainder are converted under the stimulus of insulin into fats and stored in the adipose tissue. In the case of proteins, insulin has a direct effect in promoting amino acid uptake by cells and the conversion of these amino acids into protein, additionally inhibiting the breakdown of protein that are already in the cells.

Insulin’s Effect on Carbohydrate Metabolism:
Immediately following a high carbohydrate meal, the glucose that is absorbed into the blood stream causes a rapid secretion of insulin (an insulin spike), this in turn causes a rapid uptake, storage and use of glucose by the muscles, adipose tissue (fat) and the liver as well as other tissues of the body.

Insulin’s Effect on Liver Uptake, Storage and Use of Glucose:
After a meal, insulin channels most of the glucose absorbed from the meal to the liver to be stored in the form of liver glycogen. Between meals when blood glucose levels fall, insulin secretion decrease rapidly, causing the liver glycogen to be split back into glucose, which is then released back into the blood stream to balance blood glucose levels. When the quantity of glucose being transported into the liver exceeds what can be stored as liver glycogen, insulin promotes the conversion of this excess glucose into fatty acids. These fatty acids are then converted to Triglycerides in very low-density lipoproteins and transported by the blood stream to the adipose tissue and deposited as fat.

Insulin’s Role in the Increased Metabolic Use of Fat:
All aspects of fat breakdown and use as energy are greatly enhanced by an absence of insulin. In the absence of insulin the enzyme hormone sensitive lipase in that fat cells becomes activated, causing hydrolysis of the stored triglycerides, releasing large quantities of fatty acids and glycerol into the blood stream. The free fatty acids then become the main source of fuel to be burned as energy. So in the absence of insulin the fat stores are burned as well as a free fatty acids being released into the blood stream for use as an energy source. We must also remember the importance of free fatty acids and their role in relation to muscle. Low serum FFA (free fatty acid) levels increase muscle glycogenolysis (muscle breakdown), this is especially crucial during exercise.

So as you can see, insulin has several effects that lead to fat storage in adipose tissue. Insulin increases the use of glucose by most of the body’s tissues, which in turn decreases the use of fat as an energy source. Insulin also promotes fatty acid synthesis, where in the amount of carbohydrates ingested exceeds the amount that can be utilized for immediate energy, the excess becomes the substrate for fat synthesis.

Storage of Glycogen in Muscle:
After a carbohydrate meal, insulin also transports glucose into the muscles. If the muscles are at rest and not under the rigors of exercise, the glucose is stored in the muscles in the form of muscle glycogen. The glycogen can be used for energy by the muscles at a later time.

Insulin’s Effect on Glucose Metabolism in the Muscle:
At rest, muscle tissue depends on fatty acids for its energy, not glucose. During periods of exercise however, the muscle use large amounts of glucose that do not require large amounts of insulin to activate this process, due to the muscle fibers becoming more permeable to glucose under the contraction process of the muscles during exercise.

Stimulating Insulin and its Effects on Protein Synthesis with Amino Acids:
In addition to stimulating insulin secretion by excess blood glucose as in the case of high amounts of carbohydrates, insulin can be stimulated with the amino acids arginine and lysine. The effect differs from glucose stimulation in that the amino acids being taken in the absence of a rise in blood glucose cause only a slight rise in insulin secretion, not a spike. The stimulation of insulin secretion by the amino acids arginine and lysine, create a purposeful response wherein the insulin promotes the transportation of amino acids into the muscle tissue for the intracellular formation of protein. Just as insulin is essential in the utilization of carbohydrates, so it is for the utilization of amino acids as well, but with far less insulin being necessary. So to control more stable insulin secretion, avoiding high insulin spikes, is far more advantageous for maximizing protein synthesis, maximizing fat burning and minimizing fat storage. Therein supporting the use of low glycemic index and low glycemic response nutrients for athletes seeking optimal performance and results.

Furthering the Effective Use of Amino Acids in Conjunction with Controlled Insulin Secretion:
Supplementing the intake of the amino acids alanine and arginine after the ingestion of a protein meal that is low in glycemic response stimulates the release of glucagons, a hormone secreted by the alpha cells of the islets of Langerhans in the pancreas. Glucagon activates adipose cell lipase, making increased quantities of fatty acids available to be utilized as energy and it also inhibits the storage of triglycerides. Therein supporting the advantageous fat burning process, while minimizing increases in stored fat. This stimulation of glucagon by the amino acids alanine and arginine is the same effect as stimulating insulin secretion with the amino acids arginine and lysine and in this instance, the glucagons and insulin responses are not opposites.

Applying Low Glycemic Index and Low Glycemic Response to our active lifestyle:

1. Low Glycemic Index foods may confer an advantage when eaten before prolonged strenuous exercise by providing a slow-release source of glucose to the blood without the accompanying insulin surge.
2. Low Glycemic Index foods may prolong endurance during strenuous exercise by inducing less Postprandial hyperglycemia and hyperinsulinemia, lower levels of plasma lactate before and during exercise, and by maintaining plasma glucose and FFA’s (free fatty acids) at higher levels during critical periods of exercise.
3. Low Glycemic Foods may positively affect maximal performance following sustained exercise due to low glycemic index foods maintaining a higher plasma glucose level at the end of 2 hours of strenuous exercise than that of high glycemic foods, which may have better supported subsequent maximal effort.
4. Low Glycemic Index foods support higher plasma FFA concentrations and more stable glycemic and insulinemic response. This equates to:
A. Low plasma FFA’s (or reduced FFA availability) increases or enhances muscle glycogenolysis (or muscle breakdown).
B. More stable glycemic response and insulinemic response relate to less carbohydrate oxidation resulting in more stable blood glucose levels therein reducing insulin spikes which inhibit muscle growth and promote fat storage.

So in closing, I hope you have a better understanding of the application of Low Glycemic Index and Low Glycemic Response in regards to sports nutrition and optimizing your potential. It isn’t simply identifying and eating foods with a low glycemic index number, it relates more to that foods glycemic response and the interaction with other foods. The purpose of this article was to educate you on the importance of insulin as it relates to your performance and how a better understanding of the glycemic index and glycemic response of the foods or nutritional supplements you consume can help you reach your full potential. With all of this laid out before you, it should become more evident why using a precision blended protein with a known glycemic response, or supplementing your diet with an oxidation regulator (taken with your carbohydrate meals) could be more beneficial to maximizing your performance and achieving your athletic goals.