↑Wasserman DH (January 2009). "Four grams of glucose". American Journal of Physiology. Endocrinology and Metabolism. 296 (1): E11–21. PMC2636990. PMID18840763. doi:10.1152/ajpendo.90563.2008. Four grams of glucose circulates in the blood of a person weighing 70 kg. This glucose is critical for normal function in many cell types. In accordance with the importance of these 4 g of glucose, a sophisticated control system is in place to maintain blood glucose constant. Our focus has been on the mechanisms by which the flux of glucose from liver to blood and from blood to skeletal muscle is regulated. ... The brain consumes ∼60% of the blood glucose used in the sedentary, fasted person. ... The amount of glucose in the blood is preserved at the expense of glycogen reservoirs (Fig. 2). In postabsorptive humans, there are ∼100 g of glycogen in the liver and ∼400 g of glycogen in muscle. Carbohydrate oxidation by the working muscle can go up by ∼10-fold with exercise, and yet after 1 h, blood glucose is maintained at ∼4 g.