Summary Lipid metabolism was studied in pigs fed diets containing corn oil, lard, tallow, coconut oil, or medium-chain triglyceride (MCT). The ingestion of diets containing tallow, lard, corn oil, or coconut oil resulted in approximately a 50% depression in the capacity for fatty acid synthesis in adipose tissue as measured by the incorporation of glucose-U-14C into fatty acids. The ingestion of MCT resulted in a significantly lower rate of fatty acid synthesis than observed in adipose tissue from the pigs fed the control diet, but MCT was less inhibitory than the other sources of fat. The activities of malic enzyme and citrate cleavage enzyme were significantly reduced by all fat sources except MCT. Plasma cholesterol levels were increased by feeding 10% dietary corn oil, tallow, lard, or coconut oil as compared with the pigs fed low-fat control diets. Pigs ingesting MCT-supplemented diets had plasma cholesterol levels similar to those of pigs consuming the low-fat diet. The ingestion of 10% MCT resulted in a 5-fold increase in plasma ketone levels. A hypothesis is discussed to explain the metabolic consequences of MCT ingestion in the pig.