Learn More about Energy Adjustment

[glossary term:] Energy adjustment is an analytic method by which nutrient and food group intakes are evaluated in relation to total energy intake. Energy adjustment methods are used for two primary reasons:

  • They account for the fact that total energy requirements are related to body size, metabolic efficiency, and physical activity, thereby providing a measure of diet composition.
  • They are useful in mitigating the effects of [glossary term:] measurement error in data collected using self-reported dietary assessment instruments.

A common method to accomplish energy adjustment is to calculate [glossary term:] nutrient density. For macronutrients (protein, carbohydrate, fat, and alcohol), nutrient densities are expressed as proportion of energy (i.e., % kcal from fat). For micronutrients or food groups, nutrient density is often expressed as intake (in appropriate units)/1000 kcal.

Another frequently used energy adjustment method is the residual method. In this method, the energy-adjusted intake estimate is the residual from a regression model in which total energy intake is the independent variable and absolute nutrient intake is the dependent variable. Thus, the residual is an estimate of nutrient intake uncorrelated with total energy intake and directly related to overall variation in food choice and composition.

Energy-adjusted macronutrient variables allow for the evaluation of the effect of varying dietary composition on associations between diet and health [glossary term:] outcomes. Because higher absolute energy intakes also tend to result in higher intakes of food groups and micronutrients, energy adjustment of such dietary components aids in assessing dietary composition/quality and controlling for the confounding that would result if total energy intake is associated with disease risk.

The rationale for using energy adjustment to adjust for measurement error (see Key Concepts about Measurement Error) in diet and health studies is based on the assumption that individuals tend to [glossary term:] misreport intakes of most reported foods and beverages to a similar degree and in the same direction. Although this assumption does not hold up perfectly (for example, it appears that less healthy foods tend to be [glossary term:] underreported to a greater degree than are healthy foods), evidence suggests that the assumption is reasonable. It is generally accepted that energy adjustment is advantageous in analyses of diet-disease associations and therefore, it is nearly always used, especially when a food frequency questionnaire (FFQ) is the main dietary assessment instrument (see Food Frequency Questionnaire Profile). It also is frequently used in [glossary term:] validation studies for FFQs (see Key Concepts about Validation). In general, results from validation studies show that [glossary term:] correlations between a main dietary assessment instrument and a reference instrument are higher using energy-adjusted nutrients and food groups than for non- energy-adjusted nutrients and food groups. Energy adjustment is not possible for screeners because they do not assess total energy intake (see Screeners Profile).

For More Information

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