Atwaterfaktort

Atwaterfaktort refers to a system of estimating the metabolizable energy of food, primarily used in animal nutrition and sometimes in human nutrition. It was developed by Wilbur Olin Atwater and his colleagues in the late 19th and early 20th centuries. The core principle of the Atwaterfaktort is that different macronutrients provide different amounts of energy. Specifically, it assigns a general caloric value to carbohydrates, proteins, and fats.

The standard Atwater factors are approximately 4 kilocalories per gram for carbohydrates, 4 kilocalories per gram for protein, and 9 kilocalories per gram for fat. These factors are derived from studies that measured the heat produced by the complete combustion of these nutrients. However, the system accounts for the fact that not all energy in food is absorbed or retained by the body. Protein, for instance, contains nitrogen which is excreted and represents a loss of energy. Therefore, the factors are empirically determined values that represent the metabolizable energy available to the organism rather than just the gross energy of the foodstuff.

While the Atwater system is a useful approximation, it has limitations. The actual metabolizable energy can vary depending on factors such as the specific type of food, the animal species or individual, and digestive efficiency. More precise methods, such as direct calorimetry or bomb calorimetry combined with fecal and urinary energy analysis, can provide more accurate energy values but are more complex and costly. Despite these limitations, the Atwaterfaktort remains widely used due to its simplicity and practicality in formulating diets and assessing nutritional content.