General and Chemical Definition of Fats
It was recorded in history that man uses fats to induce light and warmth for their shelter and use fats as lubricants for their instruments/tools. Man has even used fat for beauty purposes.
Food is the major use of fat to man. However it appears that there is no set quantitative requirement of fat in human nutrition probably in various cultures of human. For example, only 3% of total calorie intake by Japanese soldiers in wartime while 6%-10% of total calories as fat in general Japanese population. In America, almost 40% of the total calories as fat are intake which is an excessive quantity according to some authorities.
Nevertheless, the Food and Nutrition Board of National Research Council, American Heart Association and American Medical Association only recommend 30% below of total calories as fat and 1%-2% of essential fatty acid and linoliec acid. There is no specific dietary requirement for fat in human body for it seems to function on wide ranges of fat intake.
Fats are defined as a group of organic substances such as oils, fats, waxes and related compounds. Lipids are greasy to touch and insoluble in water but can be soluble in ether and alcohol. The food sources of fats are butter, margarine, salad, bacon, oil, salad dressing and cream. Hidden fats include egg yolk, meat fats, olives, nuts and avocados.
Fats are defined according to carbon, hydrogen and oxygen as their basic structure elements. These elements are also the same elements that comprise the structural elements of carbohydrates. But in fats the relative content of hydrogen is higher. Fats are potential ester of fatty acid and one of these is ester—a compound of an alcohol and an acid. This utilizes the metabolism of living organisms.
Reference: Nutrition and Diet Therapy (Third Edition) by Sue Rodwell Williams.