Glycemic Index in Sports Nutrition

　　The blood glucose response during eating is a key factor in health, performance, recovery and body composition

　　simply put

　　Glycemic Index is a scale that sorts foods according to their digestion and absorption speed, thereby changing blood sugar levels

　　Low-glycemic index foods and diets are generally associated with better health in terms of promoting low body fat loss and reducing the likelihood of weight gain, and are also important for the prevention and control of heart disease, obesity, and diabetes.

　　Because the blood sugar level affects the metabolic process before, during and after exercise, the glycemic index is a key concept in sports nutrition.

　　In short, a low-glycemic index and high-carbohydrate diet are the best choices for refueling before the game; a high-glycemic index and high-carbohydrate diet are the best choices for refueling after a short recovery time; Fat athletes are beneficial.

　　Background

　　was originally described in the early 1980s. The glycemic index (GI) 1 ranks foods according to their influence on changes in blood glucose levels within minutes and hours after eating, especially foods containing carbohydrates (CHO). When eating any form of CHO, the digestion process breaks down the food into single sugar units, which are absorbed into the blood and appear in the form of glucose (the most common form of blood sugar). The GI level of food (relative to the effect of eating white bread or glucose is 1-100) reflects the digestion and absorption speed of food or CHO, and changes the blood sugar level. High-grade foods are digested and absorbed faster, leading to a rapid spike in blood sugar, while low-grade foods are digested and absorbed slowly, leading to gradual absorption. Blood sugar continued to rise (Figure 1). In short, the faster the blood sugar rises, the higher the index rating.

　　The GI of food or mixed meals mainly depends on the amount and type of CHO, but there are also other factors that affect the GI, such as the content of macronutrients (CHO, protein, fat, fiber) in the food, food particle size, cooking technology, food processing, fructose or The presence of lactose, the form of starch, the presence of anti-nutrients (such as phytic acid and lectins), the metabolic health of the tested individual, etc.

　　Because the international GI table is based on the measurement of a single food, one area of ​​discussion is the ability of a single food to predict the blood sugar response of a single food to a mixed meal based on the GI of a single food. Therefore, a related concept called glycemic load (GL) was proposed as a method to characterize the blood sugar effect of a meal or the entire diet. GL is defined as the weighted average of the dietary GI multiplied by the percentage of total CHO energy. So GL reflects the amount of GI, and the amount is still one meal.

　　A common example used to illustrate the difference between GI and GL is watermelon. Watermelon has a high GI (72), but only 6 grams of CHO (120 grams of watermelon) per serving. So the GL of watermelon is low. In other words, although this is a high-GI food, you must eat a lot of watermelon before any significant changes in blood sugar levels occur. Figure 2 lists examples of each type of geographical indication food. Among sports nutritionists, health professionals, consumers, and athletes, people are interested in the effects of dietary GI on athletic performance, health, and well-being. One of the reasons for this interest is that, generally speaking, the release of insulin hormones is directly proportional to the relative increase in blood glucose levels after meals. Insulin is an essential hormone for regulating blood sugar balance, but it can play a variety of metabolic effects in the body, including stimulating CHO storage in muscles (glycogen synthesis), stimulating muscle growth (protein synthesis), preventing lipolysis (lipolysis), and stimulating fat Storage (lipogenesis). In short, foods with low GI and hypoinsulinemia (insulin release) are generally considered to be more favorable choices, because by preventing rapid blood sugar fluctuations (hyperglycemia, hunger, and sugar collapse), they (1) promote better High fat burning and fat loss rate, (2) provide a more lasting feeling of fullness; promote the stable and sustained release of energy, which is positive for both physical and mental performance. The following introduces some of the main points in the recent scientific literature, as well as the details of how the concept of active oxygen is applied to active oxygen nutrition.

　　The role of the gastrointestinal tract in affecting body composition and metabolic health

　　Generally speaking, it is best to maintain a relatively stable blood glucose concentration throughout the day. It is believed that this can prevent the many consequences of sugar "spikes" and "collapses", such as mood swings, sleepiness, hunger, and food cravings, while reducing fat storage and promoting fat oxidation (burning) (Figure 3). Therefore, low gastrointestinal foods help to stabilize blood sugar levels and provide energy at a constant rate within a few hours. On the other hand, foods high in the gastrointestinal tract may cause rapid blood sugar fluctuations and "reactive" hypoglycemia (a sudden drop in blood sugar) in some susceptible people.

　　The scientific literature on the health effects of dietary gastrointestinal tract can be summarized into two major themes: (1) Observational research, comparing the dietary gastrointestinal tract of a large number of people with the disease incidence of this population; and (ii) intervention Studies in which the use of high gastrointestinal foods instead of healthier low gastrointestinal diets can reduce the gastrointestinal tract of an individual's diet.

　　Observational research evidence shows that compared with low gastrointestinal diet, long-term consumption of high gastrointestinal diet with higher triglycerides and higher HDL (good) cholesterol, fatty liver, weight gain, obesity and pregnancy, and Type 2 diabetes risk is related. 2, 3, 4, 5. On the other hand, when individuals switch to a low gastrointestinal diet, a meta-analysis of clinical trials (a review article that uses a statistical model to calculate the impact of interventions on a given result) supports clinical research on a low gastrointestinal diet. Weight loss, prevention of heart disease and management of hyperlipidemia, prevention and treatment of diabetes6,7 For example, compared with a high-GI or low-fat diet, a low-GI and GL diet can reduce body weight by about 1 kg and reduce total fat1 Kg, the body mass index decreased by 1.3 units 7. Interestingly, from a weight management perspective, some of the reasons why low-GI diets have a beneficial effect on body composition may be because they promote satiety (ie, reduce appetite) when they last longer than high-GI diets. Eating before exercise will burn a lot of fat during exercise. Now, in weight management, managing the amount and type of macronutrients to optimize fat burning during rest and exercise has become a realistic strategy. In short, by switching to low-GI foods and supplements, you can better control or even reduce body fat, because you can better control your appetite, delay hunger, reduce fat storage, and burn more easily during rest. In motion.