MEASURES REGISTRY USER GUIDE
Conceptualizing Individual Diet
For the purpose of this User Guide, dietary behavior is conceptualized primarily as dietary intake, though related dietary behaviors and attitudes (e.g., frequency of snacking) that may be relevant to the study of childhood obesity are also addressed. Generally speaking, dietary intake refers to the foods, beverages and, potentially, supplements consumed by individuals and populations. In conjunction with information on intake, there is often interest in the context of eating, such as when, where, and with whom meals and snacks are consumed, as well as other activities during eating, such as use of digital devices. Many of the measures within the Registry focus on quantitatively assessing intake, for example, using 24-hour dietary recalls, dietary records, food frequency questionnaires, or screeners, for the purposes of arriving at estimated consumption of foods, food groups, and nutrients, or characterizing dietary patterns. For example, within the context of childhood obesity research, there is significant interest in quantifying consumption of sugar-sweetened beverages, including fruit drinks, flavored milks, soda, and energy drinks. The measures within the Registry are primarily those that involve self- (or proxy-) reporting of intake; however, objective methods for assessment are also briefly described in Section 5.
As outlined in the Measures Registry User Guide: Individual Physical Activity, physical activity is not directly measured in the same way that characteristics such as weight and height might be. The term, assessment, which “refers to an appraisal or judgement,” can be used to differentiate from measurement, which “involves collecting specific information about an object or event and typically results in the assignment of a number to that observation.” Similar to physical activity, the measurement of dietary intake is typically referred to as assessment.
In assessing intake, researchers are interested in capturing specific items consumed, along with details such as how they were prepared and the quantities in which they were consumed. As noted in Section 1, such data are typically collected at the level of individuals, with inferences made at the level of groups or populations. With the necessary details to characterize foods and beverages, data collected from individuals can be linked with food composition and related databases to estimate intakes of foods and food groups, nutrients, and other dietary components. These estimates can be used to characterize dietary intake among populations or subpopulations (e.g., prevalences meeting recommendations related to nutrients or food groups), examine influences (e.g., age, gender, socioeconomic status, education) on dietary intake, assess associations between dietary intake and outcomes (e.g., factors associated with body weight), and investigate the impacts of interventions (e.g., nutrition education, taxation of sugar-sweetened beverages) on intake.1
In addition to capturing details on the types of foods and beverages consumed, researchers and practitioners aim to understand how often different foods and drinks are consumed so that usual intake can be estimated. This is because primary interest is not typically in consumption on a given day (i.e., acute intake), but rather habitual or long-term intake over a given period of time. For example, in surveillance, researchers and practitioners are interested in whether individuals and populations meet food group recommendations and nutrient requirements on average over time, and in epidemiology, researchers seek to examine associations between usual diet and subsequent health- or disease-related outcomes. In some cases, such as some specific intervention studies, intake on a given day may be of interest. However, usual intake is typically of interest and is the focus of this User Guide.
Other measures within the Registry are intended to capture related behaviors, such as the frequency with which individuals visit fast food restaurants or consume snacks or meals while watching television. In addition, some measures capture eating attitudes (e.g., willingness to try new foods), food preferences (e.g., for salty or sweet foods), avoidance of particular dietary components (e.g., fat), diet knowledge and perceptions (e.g., regarding foods marketed as healthy), and other constructs that may influence eating patterns and body weight. Generally, measures within the Registry that include constructs such as attitudes also include some assessment of intake (e.g., a measure of attitudes toward fruits and vegetables may also query intake of fruits and vegetables). For some research questions, it may be necessary to use measures of dietary intake together with measures focused on related behaviors and attitudes.