This chapter discusses fats, which are a concentrated source of energy. If the energy intake exceeds energy requirements, excess of fat is deposited in the body. Most of the dietary fats consist of triglycerides. Chemically, triglycerides are esters of glycerol and fatty acids. Specific fats or their derivatives also form components or precursors of cell membranes, myelin, steroid hormones and prostaglandins. Hydrogenated vegetable oils, although a zero cholesterol food, may raise serum cholesterol because they are saturated. Essential fatty acids (EFA) are those fatty acids which serve important functions but cannot be synthesized in the body, and must therefore be supplied in the diet. The impact of atherosclerosis is felt acutely in the heart. The small quantity of fat present in cereals, pulses and leafy vegetables is sufficient to supply the minimum requirement of EFA. The fatty acid composition of membranes is influenced by the type of fatty acids present in the diet.