Sample and study design

The present cross-sectional study utilized data from the 2011–2012 National Nutrition and Physical Activity Survey (NNPAS), which was conducted nationwide by the Australian Bureau of Statistics (ABS) from May 2011 to June 2012. The survey employed a multistage stratified area probability sampling design to recruit participants. Detailed descriptions of the survey’s rationale, design, and methods can be found in previous literature²². In summary, the survey included private households across all Australian states and territories, including both urban and rural areas. For each participating household, one adult (aged 18 years or older and a regular resident) and, if applicable, one child aged 2–17 years were randomly selected. Sociodemographic, dietary, and anthropometric information were collected from participants during an in-person interview²².

The final sample comprised 9,519 households, representing a household response rate of 77%. In total, 12,153 participants were selected from these households. Among them, 1,101 were adolescents between the ages of 12 and 18 years. Adolescents aged between 12 and 18 years were selected to align the findings of our study with the 2013 Australian Dietary Guidelines, which provide dietary recommendations for adolescents within a similar age range²³.

The Census and Statistics Act 1905 provides ethics approval for the ABS to conduct the household interview components of health surveys²⁴. As this study involves the secondary analysis of pre-existing and nonidentifiable data, an exemption from ethics review was approved by the Deakin University Human Research Ethics Committee ([DUHREC]; application 2023 − 193).