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For further information, you might want to have a read through the USDA's FAQ's about food composition analysis

.. http://www.nal.usda.gov/fnic/foodco...letins/faq.html

In particular this section:

Quote:

I multiplied protein, fat and carbohydrate values by 4-9-4, but my energy value is different from USDA's. Why?

Calorie values are based on the Atwater system for determining energy values. The factors used in the calculation of energy in the database are given in the food description file of the USDA Nutrient Database for Standard Reference, Release 13. The basis and derivation of these factors are described in

Merrill, A.L. and Watt, B.K. 1973. Energy Value of Foods...Basis and Derivation. Agriculture Handbook No. 74. U.S. Government Printing Office. Washington, DC. 105p.

This reference is out of print, but a scanned copy is viewable on our home page. It may also be available at many university libraries. The Atwater system uses specific energy factors which have been determined for basic food commodities. These specific factors take into account the physiological availability of the energy from these foods. The more general factors of 4-9-4 were developed from the specific calorie factors determined by Professor Atwater and associates. For multi-ingredient foods which are listed by brand name, calorie values generally reflect industry practices of calculating calories from 4-9-4 kcal/g for protein, fat, and carbohydrate, respectively, or from 4-9-4 minus insoluble fiber. The latter method is frequently used for high-fiber foods because insoluble fiber is considered to provide no physiological energy. If the calorie factors are blank or zero for an item in the Database, energy was calculated by recipe from ingredients or was supplied by the manufacturer.

This clearly indicates that high fiber foods will often have the fiber pre-subtracted before calculating calories.

hth,

Doreen