The Glycemic Index (GI) referes to how fast a carbohydrate will be converted to its simplist form, glucose, and released into the blood. The faster the carbohydrate is converted to glucose the higher the GI. The slower the carb converts to glucose the lower the GI. The GI has a direct impact on blood glucose and blood insulin levels. High GI carbs cause a rush of glucose into the blood which stimulates a burst of insulin to be released by the pancreas. This insulin is meant to clear the glucose from the blood and dispose of it in the cells of the body. Low GI carbs don't cause a surge of insulin and slowly release a "glucose drip" into the blood. They're like time released energy. Insulin, though not evil, can have many neggative effects in high surges such as what happens when a lot of high GI carbs are ingested. Insulin is anti-lipolytic. It turns off the machinery used to break down body fat and use it for energy. It also, in eccessive amounts, can cause hardening of the arteries and nueropathy. People concerned about thier physiques mainly stress over the fact that it inhibits fat break down. When you eat low GI carbs you greatly reduce the amount of insulin needed to shuttle the glucose to where it needs to be. This enables fat to remain dynamic and prevents the other various health ailments (diabetes) that accompany an aver worked pancreas and insulin system. Low GI carbs, because they maintain and steady blood glucose level, won't cause up and downs in energy levels like high GI carbs will. This is vital for enyone whom values thier mental and physical performance as the lethargy of a glucose crash can leave you like the rest of America....A coutch potato. Low Gi carbs are almost always whole foods, meaning they havn't been processed and thus srtipped of thier many micronutrients. Most high GI carbs and refined foods an void of much nutritional value.