The volume of information which has appeared since 1970 on energy requirements is both lopsided and limited; lopsided in that the great mass of the data on children has been acquired in the USA and the UK (countries where there may have been an immediate need for the information for long-range surveillance or for other purposes but where there was little possibility of nutritional inadequacy in the populations), and also lopsided in that the adult data illuminates such a small area of the whole picture. The information is limited not only because the groups of individuals studied are small or because they represent only tiny fractions of the populations really at risk, but also limited because of insufficient description of methods and of the individuals studied, so that proper use of the data is restricted.
Therefore we should not wish to appear too dogmatic in relation to our assessment on the reviewed literature as it affects current concepts of energy requirements, Nevertheless some moderately firm conclusions may be drawn about certain population groupings which may introduce more of a sense of realism into this important area of nutrition.
With regard to preschool children, at present there should be no alteration in energy requirements below the age of 5 y. From 5 y up to 16–18 y, some appreciable reduction could reasonably be made - perhaps a 10% reduction from age 5 y to age 12 y in girls, 15% from age 12 to age 15 (i.e. to about 8.5 MJ/day), and a near plateau of this value as the reference throughout the remainder of adolescence and through adult life (at 9 MJ/day). In boys, again the requirements below 5y should remain as now, from age 5 up to age 16 a 10% decrease appears sensible, i.e. to a value of 11.5 MJ/day.
For adults, the value of 9 MJ/day suggested for women is near enough the present requirement and integrates more or less with the data. No change is suggested for ageing - the results are too few and in any case they do not, in the main, disagree with “requirements”. Pregnancy and lactation should certainly be reassessed and considerably reduced for energy requirements.
In adult men, the findings do not point out any clear evidence for modification of present requirements. The wide variability of the findings however warrants the need for establishing a better way of differentiation than at present available between situations which may appear nominally similar.
A very strong stimulus to further research in this field is needed. Much up-to-date information is urgently required for 1) young children in the developing countries by means of large-scale integrated and carefully designed studies of food intake, 2) adolescents in both the developing and developed countries, 3) pregnant and lactating mothers, again in both developed and developing countries. It would also be very useful to have new data on both food intake and energy expenditure of adult males and females, particularly in developing countries. Energy expenditure studies would be especially helpful in allowing an appraisal of whether or not inadequate food intake exists, even though no signs of nutritional deficiency are apparent, by reason of unusually low levels of physical activity during the non-working time. Such studies are difficult and expensive to design, to carry out, and to analyse, but are potentially one of the most productive in this complex area of energy requirements.
All of these suggested research topics necessitate a scientifically acceptable methodology and a full description for the benefits of the research to be fully reaped.
Finally, it might well be that a new perspective should be looked for in designing tables of energy requirements. The whole way of life in most developed countries differs from that in most developing countries in many ways which could radically affect physical activity and therefore energy requirements. A set of tables formulated to cover Eskimos, North Americans and Europeans, African farmers, Indian peasants, tradesmen, and clerks, and subsistence farmers in S-E Asia or South America, may not be very realistic. Perhaps some sub-divisions ought to be introduced to try and cater for these enormous variations, other than by the previous device of a factor related solely to climate. Also, the rigid demarcation between light activity, moderate activity and high activity occupations, together with their quite inadequate description, ought to be abolished and a more valid scheme should be examined.
