Just like cholesterol can be divided into "good" and "bad" varieties, the rest of the fats family can be too. Dietary fats can be classified into two categories: saturated (the "bad" fats) and unsaturated (the "good" fats). Saturated fats differ from unsaturated fats in their chemical structure: unsaturated fats have one or more double carbon bonds in their molecular “backbone” and therefore fewer hydrogen atoms. Unsaturated fats come in two types: monounsaturated and polyunsaturated. Good sources of these fats come from healthy oils, nuts, seeds, fish and avocados. Studies have shown that replacing saturated fats in the diet with unsaturated fats will lower blood cholesterol and the risk of cardiovascular disease. We are advised to keep fat within 20-35% of daily calories. The real focus, however, is now squarely on the quality of fat. The U.S. population currently gets 11-12% of energy from saturated fats and that hasn`t changed much over 15 years. It is generally recommended that saturated fat not exceed 10% of the daily fat intake, but some experts suggest getting it down to 5% would be healthier target.
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides: triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure and composition. Although the words "oils", "fats", and "lipids" are all used to refer to fats, in reality, fat is a subset of lipid. "Oils" is usually used to refer to fats that are liquids at normal room temperature, while "fats" is usually used to refer to fats that are solids at normal room temperature. "Lipids" is used to refer to both liquid and solid fats, along with other related substances, usually in a medical or biochemical context, which are not soluble in water. The word "oil" is also used for any substance that does not mix with water and has a greasy feel, such as petroleum (or crude oil), heating oil, and essential oils, regardless of its chemical structure.
Fats form a category of lipid, distinguished from other lipids by their chemical structure and physical properties. This category of molecules is important for many forms of life, serving both structural and metabolic functions. They are an important part of the diet of most heterotrophs (including humans). Fats or lipids are broken down in the body by enzymes called lipases produced in the pancreas.
Examples of edible animal fats are lard, fish oil, butter/ghee and whale blubber. They are obtained from fats in the milk and meat, as well as from under the skin, of an animal. Examples of edible plant fats include peanut, soya bean, sunflower, sesame, coconut and olive oils, and cocoa butter. Vegetable shortening, used mainly for baking, and margarine, used in baking and as a spread, can be derived from the above oils by hydrogenation.
These examples of fats can be categorized into saturated fats and unsaturated fats. Unsaturated fats can be further divided into cis fats, which are the most common in nature, and trans fats, which are rare in nature but present in partially hydrogenated vegetable oils.
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