Improving the nutrition of children and reducing rates of childhood overweight and obesity have been high priorities for the New Zealand Government since 2000. The rates of childhood overweight and obesity vary by ethnic group and socio-economic status, and reducing inequalities in the burden of childhood overweight and obesity is an explicit aim of the Government. This paper aims to identify policy options that will have an impact on the economic drivers of childhood nutrition and obesity. A qualitative model of the economic determinants of childhood nutrition within a household setting is presented. The model identifies cost barriers to sufficient healthy food as a key factor in the foods purchased and consumed within a household. An analysis of New Zealand household economic and nutritional data then identifies policy options to improve childhood nutrition and reduce rates of overweight and obesity. These policy options focus on cost subsidies for non-discretionary household expenditure and reducing the price of food to increase access to nutritious foods, including fruit and vegetables.
Nutrition, physical exercise and obesity have been identified as important policy areas for the New Zealand Government since 2000 (Ministry of Health 2000), with children receiving particular attention (Ministry of Health 2003c; Ministry of Social Development 2004)2. Children who are overweight and obese are at risk of hypertension, cardiovascular disease and depression in adolescence (Pyle 2006), while in adulthood obesity is considered the main modifiable risk factor for type 2 diabetes mellitus, and a significant risk factor for cardiovascular disease and several common cancers (James et al. 1997; Ministry of Health 2006). These non-communicable diseases will impose significant costs on the public health system in future years (Ministry of Social Development 2004).
New Zealand is not alone in highlighting obesity, nutrition and physical exercise in public policy. Several European Union member states have implemented policies to reduce the future obesity burden (Caraher et al. 2006; Lang and Rayner 2005), and a similar need for government action has been identified in the United States (Cawley 2006) and Australia (Zimmet and James 2006).
According to the 2002 Children's Nutrition Survey, 9.8% of the 5-14-year-old population in New Zealand were obese, with another 21.3% overweight (Ministry of Health 2003b). The rates were not uniform across ethnic groups, with Pacific children experiencing the highest rates of overweight and obesity (females 32.9% overweight, 31% obese; males 33.9% overweight, 26.1% obese), followed by children of Maori ethnicity (females 30.6% overweight, 16.7% obese; males 19.6% overweight, 15.7% obese). Reducing the inequalities experienced in the burden of childhood obesity is an explicit aim of government policy (Ministry of Health 2000, 2003c).
This paper examines the role of household economic resources and deprivation as a determinant of childhood nutrition and childhood overweight and obesity. We then look at broad policy options to improve nutrition and reduce differences in overweight and obesity rates between ethnic and socio-economic groups.
The Causes of Overweight and Obesity
Policy interventions that include the aim of reducing inequalities must be based on a theory of the causes of the problem to be addressed and how interventions will have an impact on the problem (Swinburn et al. 2005; Whitehead 2007). Obesity in children can be viewed as the result of nutrition practices which combine biological and environmental factors, starting in utero and carrying on through the life course (Godfrey et al. 2007), which lead to an imbalance between energy consumed and energy expended (World Health Organisation 2003). Nutrition during critical periods of development may have life-long impacts on the health of an individual (Ben-Shlomo and Kuh 2002; Rush et al. 2008). Exposure to energy-dense foods during the life course can then add to the disease risk (Ben-Shlomo and Kuh 2002; Godfrey et al. 2007).
Historically, many approaches to stabilising obesity rates have focused on individual behaviour change--with limited success (Swinburn et al. 1999). In a review of policy approaches to obesity, Lang and Rayner (2005) note that policy responses should not rely on food and activity choices made by children, as "their choices are for the most part determined by features &the adult-framed environment, such as transport, culture, education, and eating habits" (Lang and Rayner 2005: 307-308). This view is supported by Drewnowski and Rolls (2005) and Caraher and Coveney (2004), who argue that factors such as class, gender, ethnicity, income and market forces governing access and food supply act to constrain individual choices. This has been shown in the Pacific Island Families Study, where almost 40% of mothers stated that when finances are constrained, food choices are also constrained (Rush et al. 2007). Within this resource-constrained environment, social practices such as gift giving to family or church remain strong and can make the financial situation in a household more difficult (Cowley et al. 2004).
Swinburn et al. (1999) suggest that people find healthy lifestyles difficult in environments that promote high energy intake and sedentary behaviours, and that "systems-based, environmental interventions are therefore needed to increase the rather modest impact of individual and public education programs" (Swinburn et al. 1999: 563). Such an intervention would consider nutrition practices within a household in the context of cultural practices, physical and economic resources, and the ability to implement changes within these environments.
A qualitative model of the social system that generates childhood overweight and obesity within households was developed for this analysis based on a narrative review of the literature. The model development was informed by complexity theory (Blackman 2006; Byrne 1998, 2005), and methods from systems theories (Checkland and Scholes 1990; Midgley 2000). Complexity theory focuses on the study of complex systems, where a "system can be any collection of objects or processes deemed to be of interest" (Gare 2000: 330). Complex systems have particular properties, including responsiveness to local context; being composed of numerous elements, including other complex systems; and behaving in a non-linear manner (Shiell et al. 2008). For this work we have focused on the complex systems around household resources (see Figure 1). A social phenomenon, such as increasing rates of childhood overweight and obesity, is seen as "emerging" from the relevant social system as a whole. Thus, to understand childhood overweight and obesity, the social system as a whole must be understood (Byrne 2005).
Literature Review Process
A narrative literature review (Mays et al. 2005) identified factors within the household setting that lead to childhood nutritional practice in New Zealand, with an explicit focus on differences in ethnic and socio-economic status. Literature searches were conducted using Medline, Academic Search Premier, Index New Zealand and PubMed, between January and March 2007. Combinations of search terms were used to highlight literature related to children's nutrition and the prevention of obesity, and were limited to the English language. To increase the relevance to New Zealand of factors identified in the literature, an inclusion preference was given to review articles and research conducted in New Zealand. In areas where comprehensive reviews were not found (such as the location of food shopping outlets), original research articles were included. In all, 33 journal papers were included in the development of a model of factors influencing nutrition within the household setting.
Mapping the System
The identified factors operating within the household setting were grouped under thematic headings (Dixon-Woods et al. 2005), and mapped as shown in Figure 1. The household setting was chosen as a focus because it is the most influential setting on childhood nutrition for primary school-aged children (Patrick and Nicklas 2005), potentially providing all meals in a day, but also showing a gradient in practice among ethnic and socio-economic groups (Utter et al. 2007; Utter et al. 2006b). The interaction between the factors in Figure 1 was inductively identified through the results presented in the literature, and therefore represents a theory of how the interacting factors lead to the childhood nutrition outcomes in New Zealand. The factors identified were:
* caregiver perceptions of food and nutrition, and parenting style
* food eaten within the household
* the agency of children (which changes with age)
* non-economic resources, such as time available for cooking and shopping
* the cost of food
* the food purchasing practices of caregivers
* the food available in the community
* the economic resources available in the household.
No direction of interaction between factors is shown in the figure, because it is assumed that within a complex social system...