Senin, Februari 19, 2007


Fat is required for the production of cell membranes, blood lipids (body fat), bile (fat emulsifier), steroids and vitamin D. Fats molecules are made up of glycerol and fatty acids.
Body fat is also instrumental in body temperature regulation as insulation. Minimum body fat percentages of 7% for men and 12% for women are recommended. Fats are also utilized for the transport and absorption of fat soluble vitamins. In addition, fats are the only source of linoleic acid which is required for skin growth and maintenance. Minimum daily requirement for unsaturated fat is 10 grams and 15 grams is preferred.
Types of Fat
Solid at room temp, raises blood cholesterol
Animal sources, coconut, palm oil
Liquid at room temperature
Plant sources
Unsaturated converted chemically to Saturated
Regular Margarine
Lowers blood cholesterol
Safflower, corn, soy, sunflower, fish
No effect on blood cholesterol
Canola, olive, peanut oils
Fats are digested by the enzyme lipase in the small intestines with the assistance of bile salts as emulsifiers. They are then transported through the bloodstream with the assistance of lipoproteins (fat + protein coating + phospholipid) and stored as triglycerides (glycerol + 3 particles of fatty acids) in fat cells. They are then released into the bloodstream as fatty acids when energy is required.
The fatty acids travel through the bloodstream and are combined with glucose to burn the combination as energy. The combination of fatty acids and glucose is necessary for energy production. Inadequate carbohydrate availability will result in incomplete fat metabolization producing unused lipids called ketones and leading to a chemical imbalance in the blood known as ketosis. Organ and muscle tissue may be metabolized to provide glucose from the breakdown of protein. Most of the weight loss that occurs by severe carbohydrate restricted diets is from water loss as the kidneys attempt to rid the body of the ketones.
Fat is essential to survival. A fat-less diet can lead to severe problems. Linoleic acid, an essential fatty acid, is used by the liver to manufacture arachidonic acid. This super polyunsaturated fat is used in cell membranes along with protein. When needed, this fatty acid is converted into a group of chemicals that regulate blood pressure, contractions in childbirth, blood clotting, peristalsis (gut motion), and the immune system. These chemicals are short lived and are manufactured locally as needed.
source : Training Manual & Certification Course, Fitness ABCs
written by Chuck Krautblatt, Personal Trainer and Aerobics Instructor
1995, 1998

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