Glycogen storage disease type I Glycogen storage disease type I Glycogen storage disease type I (GSD I) or von Gierke disease, is the most common of the glycogen storage diseases. This genetic disease results from deficiency of the enzyme glucose-6-phosphatase, and has an incidence in the American population of approximately 1 in 50,000 to 100,000 births. The deficiency impairs the ability of the liver to produce free glucose from glycogen and from gluconeogenesis. Since these are the two principal metabolic mechanisms by which the liver supplies glucose to the rest of the body during periods of fasting, it causes severe hypoglycemia and results in increased
Glycogen is referred to as "hitting the wall". Glycogen depletion can be forestalled in three possible ways. First, during exercise, carbohydrates with the highest possible rate of conversion to blood glucose (high glycemic index) are ingested continuously. The best possible outcome of this strategy replaces about 35% of glucose consumed at heart rates above about 80% of maximum. Second, through endurance training adaptations and specialized regimens (e.g. fasting low-intensity endurance training), the body can condition type I muscle fibers to improve both fuel use efficiency and workload capacity to increase the percentage of fatty acids used as fuel, sparing carbohydrate use