Atwaterfaktorer

Atwaterfaktorer, often referred to in English as Atwater factors, are energy conversion values used to estimate the metabolizable energy content of foods. They quantify the energy provided by the macronutrients—carbohydrates, proteins, fats—and by alcohol. The concept was developed by Wilbur O. Atwater and colleagues in the late 19th and early 20th centuries and has formed the basis for many food composition tables and nutrition labels.

The general Atwater factors assign energy values per gram: carbohydrate 4 kcal (about 17 kJ), protein 4 kcal (about 17 kJ), fat 9 kcal (about 37 kJ), and alcohol 7 kcal (about 29 kJ). These values are widely used in nutrition labeling and dietary calculations in many countries, with energy sometimes reported in kilojoules.

Limitations include that actual energy yield depends on digestibility, food matrix, and individual variation. Fiber, starch structure, and processing can affect energy absorption. Sugar alcohols and certain indigestible components may provide less energy than their gram weight would suggest. Some guidelines distinguish general Atwater factors from specific factors that adjust values for different foods.

In practice, Atwater factors offer a practical, standardized method for estimating energy content. More precise measurements would account for metabolizable energy and individual variability, but Atwater factors remain widely used in nutrition databases and labeling.