Frequent lunch purchases from NSW school canteens: a potential marker for children's eating habits?

Abstract

It is estimated that Australian children aged 5–16 years consume 32%–37% of their total energy intake during school hours.1 If weekend and holiday energy intakes are considered over the school year, then food and beverages consumed at school would comprise 16% of total energy intake. In addition, energy-dense foods and beverages such as spreads, packaged snacks, biscuits and fruit/cordial drinks make a greater contribution to energy intake at school compared to out of school.1 Given dietary behaviours are established in childhood and can track through to adulthood,2 the implementation of healthy canteen and nutrition policies, which regulate the food provision in schools, may support the development of healthy dietary behaviours. In NSW, a healthy canteens policy has been in place since 2005;3 however, recent studies show implementation challenges.4-6 This may have implications for public health, including rates of overweight, obesity and high junk food consumption among school-aged children.1 Using the 2015 NSW Schools Physical Activity and Nutrition Survey (SPANS) data, we explored whether purchasing lunch frequently (i.e. ≥2 times/week) from the school canteen was associated with obesity and high intake of ‘junk’ food among students (5–16-years-old). SPANS is a representative cross-sectional survey of NSW school students and the methodology is described elsewhere.7 Briefly, parents of children in primary school (children) and secondary school students (adolescents) completed a questionnaire that included the frequency of purchasing lunch from the school canteen; eating takeaway meals/snacks; dietary indicators that were summarised using a junk food index measure (JFIM);8 and days spent in moderate-to-vigorous physical activity. Students' height, weight and waist circumference were measured; age-sex adjusted body mass index (kg/m2) were categorised as healthy weight, overweight or obese;9 and waist-to-height ratio (WtHR [cm/cm]) was categorised by cardiometabolic risk as <0.5 (low) or ≥0.5 (high).10 Participating schools (n=84; 100% completion) filled out an online school environment questionnaire that included questions on the canteen and practices to encourage a healthy food environment at school.7 Most primary schools had a canteen (93.1%), 89.9% had a canteen manager and 51% addressed healthy canteens in their school plan. All secondary schools had a canteen and a canteen manager, and 49.8% addressed healthy canteens in their school plan. One-in-ten children and almost one-third of adolescents frequently purchased lunch from the school canteen (i.e. ≥2 times/week). Table 1 shows that, following additional adjustment for eating takeaway meals/snacks ≥1 time/week and physical activity (Model 2), children who frequently purchased lunch were significantly more likely to be overweight/obese (AOR 1.36 95%CI 1.13, 1.65), with WtHR≥0.5 (AOR 1.53 95%CI 1.12, 2.08), than children purchasing ≤1 time/week. Children who purchased lunch ≤1 time/week were also more likely to be in the healthy weight category. Adolescents who frequently purchased lunch were significantly more likely to have WtHR≥0.5, (AOR 1.38 95%CI 1.02, 1.85) than adolescents purchasing ≤1 time/week. The odds of frequently purchasing lunch were significantly lower among children and adolescents in the lowest JFIM tertile and significantly higher among adolescents in the highest JFIM tertile (AOR 1.49 95%CI 1.09, 2.04). The odds of children in the highest JFIM tertile purchasing lunch was attenuated by eating takeaway meals/snacks, (AOR 95%CI 1.17 (0.87, 1.67), suggesting children who regularly purchase lunch at school also tend to eat other meals and snacks prepared outside of the home, compared to children who purchased lunch from the canteen ≤1 time/week. We had no information on the type of food purchased for lunch at the school canteen, and the cross-sectional design prevents attribution of causality; however, the consistent associations among primary school students who regularly purchase school canteen lunches and unhealthy weight status is concerning. Potential explanations for these associations are that: i) the lunches purchased in the school canteen may not meet healthy guidelines; ii) these children select the less-healthy food options from the school canteen; or iii) regularly purchasing lunch from school canteens may be a marker of time scarcity in some families who default to eating away from home. The purchasing habits of school students through school canteens is unknown; however, the release of a revised school canteen strategy in NSW in 2017 includes clear expectations to plan, support and monitor implementation, providing an opportunity to develop a greater understanding on implementation challenges and students' purchasing patterns. Our findings showed a strong positive association between children and adolescents in the highest JFIM tertile and purchasing lunch frequently from school canteens. Potentially, for these children, purchasing meals/snacks outside the home is normal dietary practice, which highlights the importance of ensuring food provided by school canteens meets the healthy eating guidelines.11