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Ever since its inception, one of FAO’s primary objectives has been to assure an adequate, nutritionally sound and safe food supply. This has required periodic assessments of the food supply and its comparison with the needs of the population. To enable this, knowledge of human food requirements, both qualitative and quantitative, is required. Thus, one of the earliest and ongoing activities of FAO’s Food and Nutrition Division has been to determine the energy and nutrient requirements of humans. FAO’s first review of energy (“calorie”) requirements was made in 1949. This was followed by four subsequent reviews, the most recent being in 2001.

However, recommendations for optimal energy requirement become practical only when they are related to foods, which provide the energy to meet those requirements. This linking of energy requirements with energy intake depends on knowledge of the amounts of energy-providing components in foods and the use of a valid expression of the energy values of those components. At first glance, this may seem simple but, with the increasing number of available methods of analysis and the enhanced sophistication of the analytical methods used to determine food components, there are myriad possible options for expressing the energy value of foods. An obvious conclusion is that the standardization and harmonization of energy conversion factors is urgently needed. This conclusion is not new, and was noted more than 55 years ago by the Expert Committee on Calorie Conversion Factors and Food Composition Tables (FAO, 1947).

Expert reviews of energy requirements have not examined closely the possible implications and effects that using different expressions of energy values of foods may have on the recommendations for requirements. Hence, no expert review has yet provided guidelines on the most appropriate methodology and expression to adopt. This technical workshop was convened to examine - in depth and for the first time - the issue of the energy content of foods and how it relates to energy requirements. In organizing it, FAO adopted the long-standing philosophy of past reviews, beginning in 1949, that any conclusions and recommendations are provisional and subject to later review. However, the fact that they are provisional or tentative does not detract from their immediate practical value. The Technical Workshop on Food Energy: Methods of Analysis and Conversion Factors met in Rome from 3 to 6 December 2002 and examined a number of topics related to the various methods of analysis of macronutrients in food and the energy conversion factors used, including close consideration of various options, as well as the implications on the food and nutrition sector of any changes that may be proposed. The objectives and framework of the workshop are described in Chapter 1. The working papers from this technical workshop will be published in a special issue of the Journal of Food Composition and Analysis, to be published in 2004 (Journal of Food Composition and Analysis, in press), thus allowing a more detailed peer-reviewed literature source for many of the arguments on the various topics debated in Rome.

The recommendations of this report are tentative. Although consensus emerged regarding the need to adopt changes as new scientific evidence emerges, the workshop participants also recognized that due consideration needs to be given to the practical aspects of implementing changes that would have an impact on a wide range of stakeholders in the food and nutrition sector. FAO expects to review this topic periodically as new scientific information becomes available and the need to change the manner in which we use the new information in everyday life emerges.

I would personally like to thank the participants (listed in Annex I) for their dedication and openness in addressing the various issues in a spirit of compromise and scientific rigour. In particular, I want to thank Bill MacLean, not only for serving as Chairperson at the bequest of FAO, but also for preparing the early versions of the draft report and resolving many of the more contentious issues. Thanks are also due to Dr Penny Warwick in her role as rapporteur and for her copious and accurate notes of the discussion. She was also active in reviewing the various drafts of the report. Finally I would like to express special thanks to the FAO staff who constituted the Secretariat and carried out much of the post-workshop follow-up, which culminated in this report.

Kraisid Tontisirin
Director, Food and Nutrition Division

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