2.2. 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.