The Physics
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Energy Density of Fats

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Schraer, William D. and Stoltze, Herbert J. Biology: The Study of Life. New York: Prentice Hall, 1999: 151 "One gram of fat on the other hand, releases 9 kilocalories." 37.7 MJ/kg
"Human Nutrition". Microsoft Encarta Reference Library 2003. CD-ROM. Microsoft Corporation, 2002. "Fats, which provide 9 calories of energy per gram, are the most concentrated of the energy-providing nutrients, so our bodies need only very small amounts." 37.7 MJ/kg
Joel, Cliffe D. "Fat."World Book Online Reference Center. 23 May 2004 "Fat is a more efficient fuel than either carbohydrates or proteins. Fat can produce about 4,000 calories of energy per pound. (9 calories per gram) 37.7 MJ/kg
Wilson, Jerry. Hidden Carbs in Foods. 2003 "If the manufacturer of a food product chooses not to list glycerin and sugar alcohols as carbohydrates on a nutrition label, then the calorie count will add up differently than you would expect using the generally accepted formula of counting 9 calories per gram of fat, 4 for carbs, and 4 for protein. 37.7 MJ/kg
E.J. Hunter. "More on Those Trans Fatty Acid."Food Processing, May 1983: 35-36 "Fat contains twice the energy density of carbohydrate (9 calories per gram versus 4 calories per gram) and does not require water for storage, as does carbohydrate." 37.7 MJ/kg
Fats. Healthy Eating Club, October, 2002 "Fat is energy dense, having an at water factor of 9 kilocalories, 37 kilojoules, per gram." 37.0 MJ/kg
Fats. Wikipedia, 13 May 2004 "Fat is one of the 3 main classes of food, and approximately 38 kJ (9 cal) per gram, as compared to sugar with 17 kJ per gram or ethanol with 29 kJ per gram, the most concentrated form of metabolic energy available to humans." 38.0 MJ/kg
Collins, Anne. Fats. 2003 "Fat is a high calorie food. There are 9 calories in each gram of fat." 37.7 MJ/kg

Ever eat excess fats like chocolate when heart-broken or just watching a movie? Think twice before you reach for another piece. Because it's the most fattening of energy sources, we need very small amounts in our body. Fats have twice the amount of calories compared to carbohydrates and proteins. Even though it is fattening, fats are very useful in the body. They help build membranes that surround our cells, cushions vital organs and protects us from extreme cold or heat. But, if you have an excess intake of fatty foods, it can lead to the storing of fat. If you are active however, the fat can be used as fuel, but if you are inactive, it can lead to being overweight.

The energy density for fats is 9 cal/g, when proteins and carbohydrates only provide 4 cal/g. However, when measuring the energy content, it is converted into kilojoules. In SI units, fats has 37.7 MJ/kg while, proteins and carbohydrates have 16.8 MJ/kg.

Because fat lacks water, their energy density tends to be greater than compared to those of protein and carbohydrates. If the fat is from a plant source, such as dietary fiber, it lowers the amount of the energy density, yet it is still high in fat but also high in dietary fiber. If the fat comes from an animal source, the amount of energy density will be higher, because no dietary fiber is present.

Although fatty acids are essential to our body, somebody eating limited fat can still maintain good health. While eating too much can be a hazard. The fat may build up in your arteries and clog t hem. It may give you an increased chance of heart disease. There are certain dietary patterns that you follow where your intake of fats can only be 10%. When eating fatty acids, it's important to remember that, quality of the fat is just as important as quantity. When eating meals, lower the amount of fat coming from animal sources and increase the amount of fat coming from plant sources. This way, the energy density reduces a little, so you won't have cardiac arrest at age 40.

Ping Zhang -- 2004