Expression of energy: commentary on the case for net metabolizable energy

A change from the use of metabolizable energy (ME) to net metabolizable energy (NME) is under consideration. ME reflects the food energy available for energy expenditure (heat production) and body gain. NME reflects the maximum food energy available for body functions that require ATP, relative to glucose. For individual foods, there can be differences between NME and ME values of up to 22%. Thus NME has applicability for food labelling, especially for comparing the ‘fattening’ power of individual foods. However, the error from using ME (rather than NME) is less than 2.5% for whole diets for the majority of people. To avoid confusion, any change to NME for food labelling should be accompanied by changes to food composition tables, and by revision of current (ME) recommendations for food energy intake. Revisions of regulatory frameworks, of nutrient information panels on food labels, of educational and promotional materials relating to food energy, and of nutrient recommendations expressed in terms of energy would also be necessary, as would re-education of consumers and the workforce. This author is not convinced that the practical ramifications for so many sectors is warranted by the small increase in accuracy obtained from using NME for whole diets.