Study area selection
Five secondary schools were selected, representing a range of socio-spatial geographic segments of the city, varying size of school (based on pupil numbers), and socio-economic characteristics (represented by free school meal (FSM) entitlement. Parents/carers who are in receipt of an income-based benefit can apply for free school meals for their child.). A radius of 800 m (an approximate 10 min walk from the school gate) was delineated as the study area around each school for the purpose of examining the food environment. We used a cut off distance of 800 m representing a 10 min walk rather than 400 m representing a 5 min walk based on statistical methods initially employed by Austin et al. in their characterisation of school neighbourhood food environments in the US [
21] and subsequently employed by Ellaway et al. in their analysis of food environments around socially disadvantaged schools in Glasgow [
22]. A cut off distance of 800 m was assessed as appropriate in this study as Scottish secondary school pupils are entitled to a 40 min school lunch break and so have ample time to reach food outlets within an 800 m radius, purchase food and return to school if they walk briskly. Pupil numbers for each school ranged from 600 pupils in the smallest school to 1300 pupils in the largest. FSM entitlement varied from 12.2% to 42.2%. Average FSM entitlement across the city at the time of the research was 30%, double that for Scottish secondary schools.
Data collection
Preliminary observational scoping work in the vicinity of one of the study areas was conducted in May 2011 to establish the parameters for observational data collection. This included: identification of outlets observed as popular with pupils for the purchase of food and drinks; observation regarding length of queues at food outlets and types of food/drinks purchased; whether gender/age/ethnicity seemed to influence purchasing behaviour; and whether promotional offers (e.g. ‘two for one’, meals deals etc.) were offered by outlets. Following this scoping exercise a ‘purchase monitoring’ pro-forma was developed, piloted, refined and then utilised by members of the research team.
Between 10 am and 2 pm, on a designated Friday in September 2011, fifteen fieldworkers (two to four per study area, dependent on perceived volume of outlets) visited each of the five study areas to gather data on the characteristics of food outlets (e.g. sandwich shop, fish and chip takeaway, newsagents) and to observe which outlets appeared to be the most popular among pupils (assessed by queue length).
Fieldworkers distributed an information leaflet explaining the purpose of the research to shopkeepers/store managers in outlets prior to the data collection. A separate pupil information leaflet was also carried by researchers for issue to any pupil who became aware that s/he was being observed and asked for information.
Where possible, in addition to the use of the data collection checklist, fieldworkers engaged shopkeepers and outlet staff in conversation regarding items sold and what was perceived as popular with pupils.
Through observation in each of the five study areas during the 40 min lunch-time break, fieldworkers identified and listed popular savoury food items frequently purchased by secondary pupils. Following the fieldwork, each of the 5 fieldwork leads identified approximately 10 of the most commonly observed items that were purchased on the day of observation. As a result of this, 45 items were identified for purchasing for nutritional analysis. It was felt to be important to strike a balance between identifying the most popular items and reflecting the diversity of items seen purchased. Some study areas offered more choice in terms of outlets and therefore greater diversity of purchase options. In addition, a limited number of similar items (such as chips and curry sauce) were purchased from different outlets in order to compare their nutritional content. Chips and curry sauce (comprising chipped potatoes, similar to French fries, served with a curry flavoured savoury sauce) is a cheap, culturally acceptable and very popular lunchtime purchase widely available from many food outlets in Glasgow.
In collaboration with Glasgow City Council environmental health colleagues, sampling officers subsequently purchased the 45 pre-agreed items (one week later), recording the outlet from which the item was purchased, study area and cost of each item. Nutritional analysis of these items was conducted by Glasgow Scientific Services to compare the quality of key nutrients (energy, fat, saturated fat and salt) with Scottish nutrient standards for school lunches.
The nutrient standards for school lunches were established to ensure that a school lunch provides approximately one third of a pupil’s daily nutritional needs. When introduced, guidance for caterers on the implementation of the standards was provided. This guidance included advice on portion sizes to ensure that meals fulfilled appetites (and did not leave children and young people hungry or vulnerable to snack on confectionary or other high fat and sugar products). The nutrient standards for school lunches also set out the amount of energy, a minimum level for key nutrients and a maximum level for total fat, saturated fat, non-milk extrinsic sugars and sodium that must be provided in an average day’s school lunch (averaged over one week). For the purposes of this study, samples collected from external sources were compared with the Scottish nutrient standards for school lunches for energy (2776 kJ (664 kcals)), total fat (no more than 25.8 g) and saturated fat (no more than 8.1 g). Due to analytical techniques, the nutrient standard for Sodium (no more than 824 mg) was converted to salt (no more than 2 mg) and used as a comparator. Because the samples collected were primarily savoury (main items) data for non-milk extrinsic sugars are not provided.