Age-related increases in obesity and unhealthy eating that occur among youth are cause for concern as they are associated with increased risk of cardiovascular disease, cancer and diabetes [1–4]. Since overweight, obesity, and poor eating behaviours are prevalent among youth populations [5–7], it is important to promote healthier body weights and eating habits among youth populations.
Excessive weight gain among youth is an ongoing public health problem in Canada. For instance, data from the 2007–09 Canadian Health Measures Survey (CHMS) suggest that among Canadian youth aged 15 to 19, 31% of boys and 26% of girls are overweight or obese . This represents a dramatic population-level increase from 25 years ago where only 14% of boys and 14% of girls were considered overweight or obese . According to the World Health Organization (WHO), adequate fruit and vegetable intake is the most important dietary indicator related to weight management and disease prevention . For optimal health outcomes, the Canada Food Guide makes recommendations for teens aged 14 to 18 years pertaining to daily recommendations for the consumption of fruits and vegetable, grain products, milk and alternatives, and meats and alternatives . However, according to the 2010 Canadian Community Health Survey (CCHS), only 48% of males and 50% of females 12 to 19 years of age consumed the recommended five daily servings of fruits and vegetables . Although these national recommendations exist, data pertaining to the prevalence of youth meeting these benchmarks for grain products, milk and alternatives, and meats and alternatives are not available in the published literature. A simple tool to measure whether youth are consuming the appropriate number of servings per day for the four food groups could provide valuable insight for stakeholders developing programs or policies to promote healthy eating behaviours.
Since youth spend a large part of their days at school, schools are increasingly tasked with preventing overweight and obesity and promoting healthy eating behaviour among youth populations. However, school stakeholders are not provided with the tools or resources necessary to develop evidence-based programs related to overweight, obesity, and healthy eating [11, 12]. The COMPASS study was designed to fill this gap [http://www.compass.uwaterloo.ca]; it is a longitudinal study (starting in 2012–13) following a cohort of ~30,000 grade 9 to 12 students attending ~60 Ontario secondary schools for four years to understand how changes in school environment characteristics (policies, programs, built environment) are associated with changes in youth health behaviours. COMPASS originated to provide school stakeholders with the evidence to guide and evaluate school-based interventions related to obesity and healthy eating (as well as tobacco use, alcohol and drug use, physical activity and sedentary behaviour, school connectedness, bullying, and academic achievement). The student-level questionnaire for COMPASS has been designed to facilitate multiple large-scale school-based data collections. As such, there were key issues for measuring both weight status and dietary intake that had to be considered when the questionnaire for COMPASS questionnaire was developed.
To accurately assess and monitor weight and nutritional status among youth, researchers often rely on retrospective self-reports, requiring the recall of behaviours. While accuracy may be compromised due to recall problems or social desirability bias (i.e., misreporting on sensitive or embarrassing behaviours to appear more favourable) , any misreporting is likely to remain consistent over time . This is most important for longitudinal research and tracking youth over time (such as in the COMPASS study). While objective measures of height, weight, and dietary behaviours provide the most accurate and valid results, they are often costly, time consuming, and not feasible for use in large population-based studies . For example, objective measures of height and weight require active consent procedures and the time of a trained researcher, while those for dietary behaviours require costly machinery and may be considered invasive and impractical in non-clinical settings (i.e., doubly labeled water), or are far too tedious and outside the realm for classroom based studies (i.e., 7-day food recall). It is therefore important to develop valid tools to measure self-reported weight status and dietary behaviours (i.e., surveys, questionnaires) that offer the advantage of being quick, inexpensive, and easy to administer in large samples using passive consent procedures.
The protocol for COMPASS involves active information with passive consent procedures. This ensures representative whole-school samples to inform and evaluate program and policy decisions at the school-level. To facilitate this large-scale data collection, enable fast and accurate processing of questionnaires, and minimize labour costs and transcription errors, the student-level questionnaire needed to be in a machine-readable format. The use of passive consent and questionnaire processing protocols do not allow for objective measures of height and weight of whole school samples. This is consistent with previous large scale studies using similar methods [11, 15, 16]. As such, we needed to develop and test the psychometric properties of self-reported height and weight measures to be used in COMPASS.
To minimize the burden on schools and students and ensure survey completion in one class period (~30-40 minutes), it was necessary that the questionnaire be no more than 12 pages long. This created a challenge in selecting items to balance both the depth of the core measures associated with each behavioural outcome and the breadth of data that could be measured in each domain. Within this protocol restriction, it was not possible to use a detailed food frequency questionnaire to measure eating behaviours in COMPASS (i.e., limited to 1-page for measuring dietary intake). The purpose of this study was to assess the 1-week (1wk) test-retest reliability and the concurrent validity of the self-reported COMPASS questionnaire measures used to determine weight status and dietary intake associated with Canada Food Guide servings.