1. Introduction

Chronic energy deficiency is the most widespread nutritional deficiency, it is said to affect half the world's children. There is much concern about the situation and considerable efforts are being made to alleviate this state of affairs. Although nowadays many observers feel that tackling poverty by a redistribution of income and resources is a prerequisite to a reduction in the extent of malnutrition, food distribution programmes may ameliorate the problem. In many countries the bulk of the budgets for child nutrition goes towards nutritional supplementation. The proposition that providing food to the undernourished ipso facto improves nutritional status and well-being has not been seriously questioned until recently. There are now numerous observations and several studies indicating that, for one reason or another, the effects of nutritional supplementation are small and much less than expected. This may be a result of poorly designed and implemented feeding programmes and studies. Alternatively, it may be that our hypotheses and models of the processes involved have been unduly simplistic and inappropriate and we may be missing important effects. We are rarely fortunate to have single causes and effects, so that a combination of these two explanations is possible, indeed probable.

The aims of this paper are:

1. to review the effects of energy supplementations in chronic energy deficiency;

2. to consider why supplementation has such small effects, in particular whether better designed and implemented studies will show greater effects, or whether other outcomes should be investigated;

3. to identify gaps in our knowledge.

As a first step, the variables and components of the processes are described.