Growing up in Scotland: overweight and obesity at age 10

1. Introduction

1.1. Background and report overview

Childhood obesity currently presents one of the world's foremost public health challenges. This challenge is particularly acute for Scotland which, along with the UK as a whole, has one of the highest levels of obesity amongst OECD countries (OECD, 2014). During childhood, those who are overweight or obese have an increased risk of conditions such as hypertension, type 2 diabetes and asthma (Oude Luttikhuis et al, 2009; Waters et al, 2011). If their weight continues to be unhealthy into adulthood, they are at an increased risk of numerous conditions associated with adult obesity, not only type 2 diabetes but also cardiovascular disease, osteoarthritis and some cancers (Nathan and Moran, 2008; SIGN, 2010; Grant, Fischbacher and Whyte, 2007). Understanding, tackling and preventing childhood overweight and obesity therefore forms an important public health priority amongst Scottish policymakers and practitioners.

The Growing Up in Scotland study (GUS) has collected data which provides a unique opportunity to further understand patterns of childhood overweight and obesity and to inform policy development. Children in the first birth cohort (BC1) have had their height and weight measured at ages 4, 6, 8 and 10. A further measurement is being undertaken as part of the age 12 fieldwork over 2017/18. A previous report, published in 2012 (Parkes et al, 2012), used some of these data to identify factors associated with overweight and obesity at age 6 – around the time the cohort children had started primary school. With the children now of secondary school age, and following two further sweeps of data collection at age 8 and age 10, the study can provide new information on childhood overweight and obesity in Scotland, specifically in later childhood.

This report explores the prevalence of overweight and obesity amongst 10 year old children in Scotland and examines how this varies between children with different characteristics. It also investigates whether the level of overweight/obesity amongst 10 years olds is different than amongst 6 year olds and whether social and demographic variations in levels of overweight/obesity change during that period. Uniquely, using the longitudinal nature of the data, the report illustrates how individual weight status changes - that is, what proportion of children move into or out of overweight/obesity – and identifies the demographic, socio-economic and related characteristics associated with those changes. Specifically, the analysis explores the factors associated with becoming overweight/obese and with moving into healthy weight from overweight/obese between the ages of 6 and 10. It therefore builds on the extensive analysis undertaken in the 2012 report (Parkes et al, 2012).

The Scottish Government Health and Social Care Delivery Plan (2016) emphasises the requirement for a concerted, sustained and comprehensive approach to improving population health through targeting particular health behaviours, acting to reduce avoidable harm and illnesses and taking a population and whole life approach to prevention and early intervention. In relation to the latter aim, analysis of GUS data presents a unique opportunity to understand how prevention and early intervention may reduce the prevalence of poorer health outcomes – in this case levels of overweight and obesity – in later childhood, adolescence and beyond.

1.2. Childhood obesity in Scotland: what do we know?

Aside from GUS, there are two principal national data sources used to monitor children's weight in Scotland: the Scottish Health Survey (SHeS) and the Child Health Surveillance Programme (CHSP).

SHeS collects data on a sample of children aged between 2 and 15 years old, and includes an objective measurement of their height and weight. The most recent findings (McLean et al, 2018), which come from the 2017 survey, show 26% of children aged 2 to 15 years at risk of overweight including 13% at risk of obesity. Historic data from the survey shows that the prevalence of overweight including obesity remained relatively stable between 1998 and 2016, fluctuating between 28% and 33%. However, in recent years levels of obesity have shown a steady decline dropping from 17% in 2014. This is largely due to a decline in obesity amongst boys which have dropped from 20% in 2012 to 12% in 2017. There are clear inequalities according to children's background: children living in more disadvantaged circumstances are more likely to be overweight or obese than those in more advantaged circumstances. For example, the 2017 results show that 30% of children living in the 20% most deprived areas in Scotland were at risk of overweight/obesity compared with 22% of those living in 20% least deprived areas.

Unlike SHeS, height and weight measurements from CHSP are taken from a census rather than a sample. However, only children in Primary 1 – the first year of formal schooling when children are aged between 4.5 and 6 years – are measured. Findings from the 2016/17 school year (ISD, 2017) indicate that 23% of children were at risk of overweight and obesity. This figure is comparable to that found amongst six year olds measured as part of GUS in 2010/11; 22%^[1] were overweight including obese (Parkes et al, 2012). Indeed, similar to the SHeS data, measurements from CHSP over time show that levels of overweight and obesity amongst children in Primary 1 have remained broadly stable over the last 10 years at around 21-23%. Data from CHSP also evidence the inequality in childhood overweight observed in other data. The 2016/17 statistics indicate that 18% of children living in the least deprived 20% of areas were at risk of overweight including obesity compared with 27% of children living in the most deprived 20% of areas.

Neither SHeS nor CHSP data provides any insight into individual BMI trajectories for children. For example, to demonstrate the proportion of children who remain overweight or obese between Primary 1 and Primary 7 or how many children move into or out of overweight during that time – or any other time period. Such insight is possible using data from the National Child Measurement Programme in England which takes height and weight measurements from children in Reception year and Year 6 – their first and final years of primary school. Although national level routine linking of children's Reception and Year 6 results is not yet possible, it is possible to link individual results using locally held data. Analysis by Public Health England (Copley et al, 2017) used these data from four local authorities to examine trajectories of BMI amongst children in primary school between 2006/07 and 2014/15.

They found that most (75%) children who were healthy weight in Reception remained a healthy weight in Year 6. However, around 15% became overweight and a further 8% became obese. Amongst children who were overweight in Reception, the majority either remained overweight (30%) or became obese (43%). Around 27% returned to a healthy weight. For children who were obese but not severely obese, around two-thirds remained so, including a third who developed severe obesity. Twenty percent became overweight and just 10% became a healthy weight. Thus children already overweight or obese at entry to primary school were at significant risk of remaining so or seeing their BMI increase over the primary school period.

Similar analysis at a UK level has also been undertaken using data from the Millennium Cohort Study (Mead et al, 2016). In tracking BMI between ages 5 and 11, researchers found comparable results: 19% of children of healthy weight at age 5 had become overweight or obese at age 11; 63% of children who were overweight at age 5 remained so at age 11, including 32% who became obese; and 68% of children obese at age 5 were also obese at age 11.

1.3. Tackling childhood obesity: the policy context

As noted above, Scotland, along with the UK as a whole, has a particularly poor obesity record relative to other OECD countries (OECD, 2014). The implications of the issue are such that recent estimates of the total (direct and indirect) costs of overweight and obesity to Scottish society, including labour market related costs such as lost productivity, have been put at £0.9-4.6 billion (SPICe, 2015). The pervasiveness of the obesity problem, and the health and economic consequences of obesity, mean that tackling it remains a key priority and a major challenge for the government and its delivery partners.

Given its severity, addressing the issue of childhood obesity is a priority for the Scottish Government. At an overarching level, the National Performance Framework contains an ongoing commitment to increase the proportion of healthy weight children^[2]. Progress towards this target is monitored via a set of National Indicators which utilise data from SHeS and is supported by a range of proposals to address overweight and obesity set out in the Scottish Government's Fairer Scotland Action Plan (Scottish Government, 2016). Alongside a range of actions designed to tackle health inequalities, including new national strategies for mental health, alcohol and maternal and infant nutrition, the Action Plan proposed a new strategy on poor diet and obesity. This proposal was also committed to in the 2017-18 Programme for Government (Scottish Government, 2017).

In July 2018, the Scottish Government published A Healthier Future – Scotland's Diet and Healthy Weight Delivery Plan (Scottish Government, 2018a). The plan sets out a vision for everyone in Scotland to eat well and have a healthy weight. More specifically, it also sets an ambition to halve childhood obesity by 2030 and to significantly reduce diet-related health inequalities. Actions to tackle childhood obesity will start pre-pregnancy and continue throughout the early and school years and into adolescence. This sits alongside broader population measures to tackle conditions in the overall environment which make healthier food choices more difficult. The Scottish Government published a consultation in early October 2018^[3] to consider the promotion of discretionary foods high in fat, sugar or salt with little or no nutritional benefit and how such incentives encourage people to buy and eat more.

Recognising that the drivers of overweight and obesity are complex, multi-faceted and shaped by a broad range of factors, the delivery plan for improving diet and weight sits alongside a wide range of government policy and action. Promoting a joined up approach to public health, the Scottish Government along with the Convention of Scottish Local Authorities' (COSLA), published Public Health Priorities (Scottish Government and COSLA, 2018) which aims to focus efforts to improve the health of the population. Included amongst these is a priority to create 'a Scotland where we eat well, have a healthy weight and are physically active'. The Diet and Healthy Weight Delivery Plan is therefore designed to be considered alongside A More Active Scotland: Scotland's Physical Activity Delivery Plan (Scottish Government, 2018b). The recently published tobacco control strategy (Scottish Government, 2018c) and other forthcoming renewed public health strategies on alcohol prevention and substance use are also relevant.

The Scottish Dietary Goals (Scottish Government, 2016), revised in 2016, provide the characteristics of the diet that will "improve and support the health of the Scottish population", in part through reducing levels of obesity. Applicable to both adults and children, the goals include reducing intake of salt, free sugars and calories and increasing intake of fruit and vegetables, fibre and oil-rich fish. Amongst a range of actions aimed at achieving these goals are the Eat Better Feel Better campaign^[4] and various programmes designed to encourage people to make healthier choices in the way they shop, cook and eat. Food available in and around schools has also been a focus of policy aimed at improving children's diets. Legislation^[5] requiring local authorities to ensure schools provide food and drink of an appropriate nutritional standard has been in place since 2007 with accompanying guidance (Scottish Government, 2008). These regulations are due to be updated following a recent consultation on proposed amendments^[6]. Better Eating Better Learning (Scottish Government 2014a) provides guidance for a range of stakeholders (schools, local authorities, caterers, procurement departments, parents, children and young people) aimed at making further improvements in school food and food education through partnership working. Meanwhile, Beyond the School Gate (Scottish Government, 2014b) seeks to help the same stakeholders and other partners, influence the food environment around schools and support children and young people to make healthier choices.

Alongside a range of benefits for physical and mental health, regular physical activity helps adults and children maintain a healthy weight. A More Active Scotland: Scotland's Physical Activity Delivery Plan (Scottish Government, 2018b) sets out the Scottish Government's ambitions for a Scotland where "more people are more active, more often". Building on the Active Scotland Outcomes Framework^[7], the delivery plan sets out actions the Scottish Government and a wide range of delivery partners are taking to achieve a series of outcomes ranging from encouraging and enabling the inactive to be more active to improving opportunities to participate, progress and achieve in sport. Progress towards achieving the goal of a more active population has been made through a range of activities in recent years including the implementation of the National Walking Strategy (Scottish Government, 2014c), the Cycling Action Plan (Scottish Government, 2017b), the Active Schools programme^[8], Community Sports Hubs^[9] and the Legacy 2014 Physical Activity Fund^[10]. Of particular relevance for children and young people is the Scottish Government's commitment to expanding the Daily Mile^[11] to ensure that Scotland becomes the first 'Daily Mile nation' with roll out to nurseries, schools, colleges, universities and workplaces. Recent research results suggest the Daily Mile is effective at increasing levels of moderate to vigorous physical activity (MVPA), reducing sedentary time, increasing physical fitness and improving body composition (Chesham et al, 2018).

1.4. About the Growing Up in Scotland study

GUS is a longitudinal research study which tracks the lives of thousands of children and their families in Scotland from the early years, through childhood and beyond. The main aim of the study is to provide new information to support policy-making in Scotland but it is also intended to provide a resource for practitioners, academics, the voluntary sector and parents.

To date, the study has collected information about three nationally representative cohorts of children: a child cohort and two birth cohorts. Altogether, information has been collected on around 14,000 children and families in Scotland.

This report draws mainly on data collected at the time children in the first GUS birth cohort were aged around 6 years old and had recently entered primary school (2010/11) and at the time they were aged 10 and in Primary 6 (2014/15). More detailed information about the data is provided in section 2.1.

1.5. Research questions

Building on the analysis undertaken in a previous GUS report examining overweight and obesity at age 6 (Parkes et al, 2012), this report focuses on levels of child overweight and obesity at age 10 and changes in BMI classification over the primary school years. It addresses the following questions:

• 1. What proportion of children are overweight/obese at age 10, compared with age 6, and what proportion move into and out of healthy weight/overweight/obese categories during that period?
• 2. How does overweight/obesity vary amongst 10 year old children according to demographic and socio-economic characteristics and is there any change in the social gradient of overweight/obesity between age 6 and age 10?
• 3. What other factors are associated with overweight/obesity at age 10?
• 4. Which factors are associated with a move out of or a move into overweight and obesity between ages 6 and 10?

Prevalence of overweight and obesity among children aged 10 and trajectories of movement into and out of healthy weight/overweight/obese categories between ages 6 and 10 are considered in chapter 3. Differences in levels of overweight/obesity amongst 10 year olds according to demographic and socio-economic characteristics are considered in chapter 4 whilst differences by other characteristics are considered in chapter 5.

Chapter 6 explores what experiences and circumstances are associated with a move into or out of overweight between age 6 and age 10. Finally, chapter 7 draws together key findings from the previous chapters and suggests what implications they have for policy makers and others seeking to reduce levels of overweight and obesity amongst children in Scotland.