lipids are a general term for oils, fats, and lipids. the oils and fats in food are mainly oils and fats. generally, those that are liquid at room temperature are called oils, while those that are solid at room temperature are called fats. fat is composed of three elements: c, h, and o. fat is a triacylglyceride composed of glycerol and fatty acids. the molecule of glycerol is relatively simple, but the types and lengths of fatty acids are different. fatty acids are divided into three categories: saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. fat is soluble in most organic solvents but not in water.