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* Working group members: THOMAS (U.S.A., Chair), IMMINK (Guatemala, Co-Chair), AFONJA (Nigeria), ALLEN (U.S.A.), GALAL (Egypt), PELTO (U.S.A.).
1. Introduction
2. Designs for studying the effects of low energy intake on behavior
3. Types of variables
4. Proposed future activities with IDECG support
The currently available
data on chronic energy deficit suggest that there is a
partitioning of effects between biological and behavioral
outcomes. While much remains to be learned about the nature of
this partitioning, it is clear that further work on the
behavioral consequences of low intake is critical, given the
continuing pervasiveness of this problem.
The nature of the behavioral effects, with their ramified socioeconomic consequences, is such that research on this important topic is most appropriately pursued using designs that are community-based and focused on multiple social units. We feel that inquiry into social behavior is necessary because it provides the critical link between the biological consequences and policy implementation.
In the past it has often been the case that social policy addressing the issue of low dietary intakes has not moved forward because of lack of evidence concerning the social and economic implications of chronic energy deficit. Moreover, data have not addressed specific issues that are of relevance to particular planning ministries. For example, to be useful to a minister of education, links of chronically low intake to specific educational concerns (such as attendance, classroom behavior, student achievement, teacher job satisfaction, and other features that may be affected by low intake) must be documented.
Scientists
working in the area of nutrition and health have often assumed
that the responsibility of moving toward policy implementation
rests on their research perspectives. However, the perspective of
the community can be a powerful tool in helping to bring about
necessary changes. Therefore, community perspectives and direct
community involvement in problem definition and effective
solution implementation should be part of policy-oriented
research activities.
There are several
alternative designs that can be utilized to assess the
relationship of energy intake to behavior and to examine the
socioeconomic consequences at the level of the individual, the
household and the community. In a strict sense, it may be argued,
as the anthropologist Edward Sapir suggested many years ago, that
it is only the individual who thinks, feels, eats and acts - that
behavior is a property of individuals.
However, we are concerned here not only with the consequences of chronically low energy intake for the individual, but also with the consequences for the organization and function of households and communities in which the individual members are subjected to low intake. Thus, the research design selected must permit assessment at three levels, which is to say that the study should have the community, the household, and the individual as units of analysis.
The behavioral impact of low intake can be examined in terms of 1 ) the effects of short-term deficits of energy intake relative to usual intake/expenditure patterns, or 2) the long-term effects of chronically low intake. Since energy deficits in relation to expenditure cannot be maintained over long periods of time, the focus on long-term consequences is essentially an assessment of the effects of achieving and maintaining energy balance at low levels of energy intake. The designs that follow can be used either for the purpose of assessing the behavioral and socioeconomic consequences of achieving energy balance at low levels or identifying short-term behavioral responses.
There are
two general types of designs that are applicable:
"observation studies" and "intervention
studies". In the former type, the independent variable(s)
represent some dimensions of the economic, social and cultural
environment of the household and are measured as a phenomenon
outside of investigator control. In contrast, "experimental
studies" are characterized by a direct manipulation of the
independent variable(s).
There are two forms of
naturalistic designs that can be applied to the issue of the
"consequences of low-level energy balance" question.
One design is based on identifying the distribution of levels of
intake in a population. Individual intake is determined, and
individuals and households are classified by levels of intake.
Communities can be similarly classified by the proportion of
low-intake individuals/households.
Data collection and analysis can be based either on the full "intake/expenditure" distribution, or subjects (households) can be selected out of this distribution based on specific characteristics.
A second type of naturalistic study could be termed "natural experiment", for it is based on identifying events or conditions that alter the energy balance, either by increasing or decreasing intake and/or energy demands. In either case, the term "natural experiment" is used to emphasize the fact that the investigator does not manipulate the energy variable, but takes advantage of conditions that potentially alter energy balance. The determination that the energy balance is shifted to a different level is a primary requirement of this design.
Studies
that make use of the distribution in the population assume that
the patterns that emerge have some time depth, that they reflect
"long-term consequences" of low intake. On the other
hand, studies that utilize "natural experiments" (e.g.,
outmigration by male household members, short-term variations in
food availability or labor demand) require a longer time frame
for data collection, as do studies based on experimental designs.
The experimental
manipulation of the independent variable can theoretically focus
either on shifting intake or shifting expenditure. However, a
primary manipulation of one component may produce a secondary
level manipulation of the other.
2.2.1. Supplementation studies
The classic approach is a supplementation study, in which an attempt is made to shift intake by providing additional calories to the experimental group in the study. Follow-up studies of previous supplementation studies, such as those currently being undertaken at INCAP, also provide an opportunity to assess long-term consequences of higher levels of energy intake during early childhood.
2.2.2. Community development as an experimental intervention
While supplementation studies are an intervention on the intake side of the energy balance equation, an alternative design is to produce a change in the energy expenditure of the study population.
Typically, chronically low levels of intake occur in communities where the demands for energy are relatively high and where even the provision of basic necessities (including food, water and fuel) require considerable physical activity. To the extent that energy-saving (labor-saving) interventions become institutionalized as a permanent condition in the community, the experiment avoids the ethical problems that pervade not only experimental supplementation but also naturalistic designs, in which subjects typically receive little or nothing in return for their participation in the research endeavor.
As community development personnel know well and public health professionals are increasingly aware, interventions that are imposed or brought into a community by external agencies are rarely highly effective. Community participation is fundamental to successful community development. Thus, if an experimental design based on changing energy demand is utilized, community participation is an essential methodology for such a study.
This participation should include: a) self-assessment of problems related to chronic energy deficiency, b) designing solutions in the form of social developmental actions, and c) validation of the solutions, which in turn leads to on-going adjustment in program design and execution by the community. An explicit methodology for this level of direct community involvement needs to be developed as a prerequisite to the implementation of a study and could profitably be the subject of a workshop supported by IDECG.
An
effective design that utilizes a change in the energy requirement
to assess behavioral responses to chronically low intake must be
able to identify the separate and interactive effects of
increased time availability and increased energy availability.
Focus on specific domains of behavior (e.g., mother-child
interaction) may be an area in which the time versus energy issue
may be separable.
The consequences of a
change in dietary energy intake should be observable in one or
more of the following dimensions:
(a) Body size and composition
(b) Time allocation to different activities
(c) Intensity of activity
The measurement of these changes can be classified in terms of the following taxonomy:
1.
Intermediate behavioral variables
2. Intermediate biological
variables
3. Outcome variables
(a) Investigator-determined
(b) Community- and subject-determined
The types of variables that can be measured within this taxonomy include the following:
1. Intermediate behavioral variables
1.1. Activity patterns (time-shares among activities classified by two dimensions)
(a) Activity type
(b) Energy cost1.1.1. Instrumental (task-oriented)
- market production
- home production
- education and training (human capital formation)1.1.2. Expressive (relational)
- leisure time
- social interaction1.2. Social support network
1.3. Intrahousehold economic roles and decision-making
2. Intermediate biological variables
2.1. Body composition/growth and development
2.2. Energy intake
2.3. Health status
3. Outcome variables
3.1. Investigator-determined (etic)
3.1.1. Economic
Household income (monetary and non-monetary) expenditures (secondary effects, e.g., gardening; home improvement)3.1.2. Psychological: cognitive and psycho-motor development and social-emotional functioning
3.2. Community- and subject-determined (emic)
3.2.1. Individual level
3.2.2. Community level
4. External (community) variables
4.1. Economic; e.g., market prices of final and intermediate goods
4.2. Community infra-structure (autonomous or as a secondary effect)
It should be clear that the identified outcome variables may have secondary or multiplier effects (e.g., on the intermediate variables of energy intake, health status). The study design should fully anticipate measurement of the secondary effects over time.
In order to
define what community/subject (culturally or emically) determined
outcomes should be included, the study design must anticipate a
period of interaction with community members before actual,
pre-intervention measurements are initiated.
1. Commissioning of a
review paper on long-term social consequences for individuals,
households and communities of chronic energy deficits. This paper
should review the effects on groups living under persistent CED
as well as those exposed to fluctuating levels of CED.
2. Workshop on direct community-involvement models in problem-solving related to CED.
3. Pilot studies to develop measurement methodology and obtain a cross-cultural list of perceived needs and desired outcomes by target populations. Consideration should be given to collaboration with the network of investigators currently involved in UNU Nutrition and Primary Care Activities.
4.
Inventory of existing data sets that lend themselves to
re-analysis under one of the proposed designs and provision of
funds for computer analysis.