The liver is a critical metabolic organ that regulates energy metabolism through various processes. Glucose is metabolized to pyruvate via glycolysis and then oxidized to generate ATP through the TCA cycle and oxidative phosphorylation. In the fed state, glycolytic products are used for *de novo* lipogenesis, where long-chain fatty acids are incorporated into triacylglycerol, phospholipids, and cholesterol esters, which are stored in lipid droplets or secreted as VLDL particles. During fasting, the liver secretes glucose through glycogenolysis and gluconeogenesis. Fasting also promotes lipolysis in adipose tissue, releasing nonesterified fatty acids that are converted into ketone bodies in the liver, providing an alternative energy source for extrahepatic tissues. Liver metabolic processes are regulated by hormonal and neuronal signals, with insulin stimulating glycolysis and lipogenesis while suppressing gluconeogenesis. Glucagon counteracts insulin action. Transcription factors and coactivators, such as CREB, FOXO1, ChREBP, SREBP, PGC-1α, and CRTC2, control the expression of enzymes involved in these metabolic processes. Abnormal energy metabolism in the liver can lead to insulin resistance, diabetes, and nonalcoholic fatty liver diseases (NAFLD).The liver is a critical metabolic organ that regulates energy metabolism through various processes. Glucose is metabolized to pyruvate via glycolysis and then oxidized to generate ATP through the TCA cycle and oxidative phosphorylation. In the fed state, glycolytic products are used for *de novo* lipogenesis, where long-chain fatty acids are incorporated into triacylglycerol, phospholipids, and cholesterol esters, which are stored in lipid droplets or secreted as VLDL particles. During fasting, the liver secretes glucose through glycogenolysis and gluconeogenesis. Fasting also promotes lipolysis in adipose tissue, releasing nonesterified fatty acids that are converted into ketone bodies in the liver, providing an alternative energy source for extrahepatic tissues. Liver metabolic processes are regulated by hormonal and neuronal signals, with insulin stimulating glycolysis and lipogenesis while suppressing gluconeogenesis. Glucagon counteracts insulin action. Transcription factors and coactivators, such as CREB, FOXO1, ChREBP, SREBP, PGC-1α, and CRTC2, control the expression of enzymes involved in these metabolic processes. Abnormal energy metabolism in the liver can lead to insulin resistance, diabetes, and nonalcoholic fatty liver diseases (NAFLD).