Updating normative cross-sectional values and secular trends in body mass, body height and body mass index among Québec children and adolescents.

Objective: The main objective of this study was to examine secular trends in body mass, body height and body mass index (BMI) from measured rather than self-reported values between 1972 and 2017.

Methods: A total of 4500 students (males = 51%) were selected from a stratified sampling. The age range varied between 6.0 and 17.9 years. The sample came from 24 elementary schools and 12 high schools located in six urban cities from the province of Québec. All the tests selected were based on standardized procedures that are recognized as valid and reliable. Standardization and modeling of smoothed percentile curves for each variable for both sexes were produced.

Results: Regional variations between youth from the province of Québec and those from all other Canadian provinces confirm the relevance of using data specific to the target population. Comparisons with the 1972 and 1982 data show an important increase in body mass (~ 7 kg, i.e. 16.4%) and BMI (~ 1.4 kg·m, i.e. 19.9%) with minor change in body height (~ 1.8 cm, i.e. 3.9%). Youth from low-income backgrounds (p = 0.001) as well as those living in large urban cities (p = 0.002) see their probability of developing overweight or obesity greatly increase (low-income = 2.1 times; large urban cities = 1.3 times). However, overweight and obesity rates seem to have stabilized at around 21% since 2004.

Conclusion: This study provides up-to-date data on factors that contribute to the prevalence of overweight and obesity in youth in urban settings of Québec, and will be instrumental in guiding public health strategies designed to optimize growth outcomes.