Acute and chronic undernutrition
This supplement has been produced in response to the increasing number of reports on adult nutrition surveys received by the RNIS and the concomitant interest in the subject shown by the readership. We hope that it will help the readers of the RNIS to interpret the results of the adult nutritional surveys reported.
This article describes simple techniques suitable for the assessment of adult nutritional status in emergency-affected populations. We do not intend it as a comprehensive review of all aspects of assessing adult nutritional status, but as a guide to techniques useful in the field.
During famine-relief operations workers are increasingly recognising and treating severe adult undernutrition. There have, however, been few studies to investigate the problems associated with screening and treating severely undernourished adults during famine and consequently, little guidance is available to field workers. There is at present, no universally accepted definition or classification of acute adult undernutrition and no specific treatment guidelines for the condition. Thus the screening and selection of admissions into therapeutic feeding centres and the dietary treatment of those admitted becomes problematic. Since 1992 however, there have been several advances made in these areas and this article attempts to pull some of these together. We also make some recommendations as to the techniques suitable for the assessment of adult nutritional status under different circumstances.
All of the indicators described in this article attempt to assess adult nutritional status. It is important to realise that, to date, no consensus on a definitive method has been reached; more research is required to achieve this. None of the anthropometric indices described below can be considered to be a gold standard, although body mass index (BMI) has often, mistakenly, been treated as if it were.
This supplement focuses on the nutritional assessment of adults between twenty and sixty years of age. The assessment of older persons is a complex task and is not described in detail here 1, 2. In addition, the article does not consider the assessment of obesity, micronutrient deficiencies or pregnancy.
Appendix one provides some basic definitions of terms that are employed in the discussion of adult nutritional assessment.
There are two main patterns of undernutrition found in children. These are stunting and wasting 3, 4. Different processes produce these two patterns and they are assessed using separate anthropometric indices. In children, acute nutritional deficit and/or disease (such as diarrhoea) produce wasting, characterised by a reduction in weight-for-height or arm circumference, or both. Prolonged nutritional deficit and/or disease result in stunting, characterised by a reduction in height-for-age 5. Wasting and stunting are associated with different functional consequences. Weight-for-height is a powerful predictor of short-term mortality, as is the mid upper arm circumference (MUAC). Height-for-age predicts longer-term mortality 6, 7, 8, 9, 10.
The nutritional assessment of adults is more problematic. Despite metabolic differences between chronic and acute undernutrition 11, 12, 13, 14, the absence of linear growth removes the power of a height variable to discriminate between the two main patterns of undernutrition. In 1988, the International Dietary Energy Consultative Group proposed a definition of chronic adult undernutrition calling it 'chronic energy deficiency' (CED), clearly differentiating it from 'acute energy deficiency' (AED).
Chronic Energy Deficiency (CED) was defined as:
"A steady state at which a person is in an energy balance although at a cost either in terms of increased risk to health or as an impairment of functions and health" 14Acute Energy Deficiency (AED) was defined as:
"A state of negative energy balance, i.e. a progressive loss of body energy"14The differentiation of acute and chronic adult undernutrition is important because the two conditions entail different adaptations and have different functional consequences. For example, habituation to CED has been described in Indian labourers who, with a mean BMI of 16.6kg m-2, were able to function reasonably normally 11. By contrast, similar BMIs, rapidly induced in 32 previously well-nourished volunteers, resulted in extremely poor physical and psychological states12. Differentiating between these two types of undernutrition may be difficult with a one-off measurement. They can be distinguished using a series of measurements taken over time, but in practice, this option is often not available. As acute undernutrition wastes peripheral body tissues faster than central tissues, it may be possible to compare two different body measurements in order to differentiate between these two forms of undernutrition. It may also be that adaptation below a certain threshold for each measurement is impossible and hence those falling below that threshold must have acute undernutrition. However, at present there are few data available with which to examine these problems.
We feel that the term "energy deficiency" is unhelpful when applied to undernutrition because it obscures the importance of protein catabolism, deficiencies of vitamins and minerals. For this reason, we prefer the term "undernutrition" rather than "energy deficiency".
Primary undernutrition develops when nutrient intake is insufficient to provide for normal physiological needs. In adults, primary undernutrition is invariably due to a lack of food. Secondary undernutrition occurs when an underlying disease process (for example, HIV/AIDS, TB and cancer) increases metabolic demands and/or decreases food intake or utilisation. The treatment of primary and secondary undernutrition may be quite different.
