In modern societies, fat is consumed in much larger amounts than in countries where people are eating whole grains as their princip al food. For example, in the United States, about 42 percent of the ordinary diet is composed of fat, while in rural Mexico among the Tarahumara, a native people renowned for their health and longevity, the amount is only 12 percent. About 15 percent of the standard macrobiotic diet consists of fat. Lipids are the family name for fats, oils, and fatlike substances including fatty acids, cholesterol, and lipoproteins. Fats are solid at room temperature, while oils are fluid.
Solid lipids tend to contain more saturated fatty acids.
Fatty acids are long chains of carbon and hydrogen atoms including an oxygen molecule at one end. Saturated fatty acids are bonded or saturated to hydrogen atoms. Unsaturated fatty acids lack at least one pair of hydrogen atoms. Polyunsaturated fatty acids are those in which more than one pair is missing. Fatty acids are the building blocks of fats, just as simple sugars are the fundamental units of carbohydrates.