Lipid metabolism encompasses the synthesis, transport, modification and breakdown of fats that are essential for energy homeostasis and cellular structure. It involves dietary lipids, primarily triacylglycerols and cholesterol, as well as lipids synthesized in the liver and other tissues.

After ingestion, lipids are emulsified, digested into fatty acids and monoacylglycerols, then reassembled and packaged into chylomicrons for transport through the lymph and blood. The liver plays a central role by synthesizing triacylglycerols, phospholipids and cholesterol, assembling them into very low density lipoproteins, and converting lipoproteins through a cascade that includes low density and high density particles. These particles coordinate lipid delivery to and from peripheral tissues.

Within cells, fatty acids are activated to acyl CoA and transported into mitochondria for beta oxidation, a cyclic pathway that shortens acyl chains, producing acetyl CoA, NADH and FADH2. Acetyl CoA enters the citric acid cycle or serves as a precursor for ketone bodies during fasting. In contrast, fatty acid synthesis occurs in the cytosol, building long chains from acetyl CoA using malonyl CoA and NADPH, under the control of key regulatory enzymes sensitive to hormonal and nutritional status.

Regulation integrates endocrine signals, particularly insulin, glucagon and catecholamines, with cellular energy sensors. Imbalances in these pathways contribute to obesity, insulin resistance, non alcoholic fatty liver disease, atherosclerosis and dyslipidemia. Current research investigates molecular regulators, including transcription factors, enzymes and transport proteins, as well as the impact of diet, microbiota and pharmacological agents on lipid handling and cardiometabolic risk.