Methodological considerations

1. At present, the doubly-labelled water technique provides the most exact quantitative measurement of total energy expenditure of free-living individuals.

2. Minute-by-minute heart rate monitoring techniques are promising, less costly and more accessible, and should be validated more extensively in children against the doubly-labelled water method.

3. Time and motion activity diaries can be used to estimate the energy expenditure of children, but the energy cost of activities used to calculate energy expenditure should be specific to the child's age and sex. Time and motion activity diaries should also be validated in children in the field against the doubly-labelled water method or against minute-by-minute heart rate monitoring if the latter is considered acceptable, as described in the preceding paragraph.

4. Dietary energy intake surveys can be used to estimate the adequacy of diets. Intake data should be derived from representative population samples, and screened and edited to exclude data incompatible with fundamental principles of energy physiology.