Hepatic Glycogen and Fat Oxidation

Excessive fat in the liver is associated with impairments in metabolic health. Low levels of DNL and high levels of hepatic fat oxidation are considered to be protective. A decrease in glycogen stores has been causally linked to improved whole body fat oxidation. Also on an organ level, it is suggested that hepatic fat oxidation is stimulated by low hepatic glycogen stores. Next to hepatic fat oxidation, DNL may be influenced by hepatic glycogen stores. Some studies have shown that prolongation of fasting time lowers hepatic glycogen content. It is therefore hypothesized that prolonging fasting time will lower glycogen content and thereby increases fat oxidation and decreases DNL in the liver. To this end, hepatic fat oxidation (plasma marker beta-hydroxybutyrate), de novo lipogenesis, hepatic glycogen content and intrahepatic fat content, will be measured upon a short overnight fast and an extended overnight fast in 13 overweight/obese subjects with hepatic steatosis.