The prevalence of overweight and obesity is rapidly increasing in children and adolescents, making these groups important targets for prevention. Promoting healthful dietary patterns is likely to contribute to preventing the onset of overweight and obesity. To effectively prevent or modify obesity-inducing eating patterns, a detailed understanding of factors that determine these behaviors is essential.

Environmental influences in childhood eating patterns

Until recently, the research of determinants of dietary intake in youth has predominantly been focused on individual level determinants, such as attitudes and social influences. More recently a shift in attention to environmental determinants has occurred. A major driving force for the increasing obesity prevalence may be an environment that encourages eating and discourages physical activity^{[1, 2]}. Child and adolescent dietary behavior is likely to be strongly influenced by environmental factors. Parents decide on what kind of foods they offer their children^[3]. Adolescents become more autonomous, and lifestyle, social and environmental changes take place. School food environments may have a large impact on adolescent food choices^[4-6].

The environment can be defined as ‘anything outside the individual’. Several types of environmental factors can be distinguished, such as physical factors (built environment, availability of foods), socio-cultural factors (social influences), economic factors (household income) and political factors (rules and regulations). These factors can be categorized in several environmental settings, such as microenvironments where groups of people meet (home, school, and restaurant) and macroenvironments that include the broader infrastructure that may support or hinder health behaviors (town planning, transportation infrastructure). For example, availability of vegetables (physical factor) can be important in various microenvironmental settings: availability of vegetables at home or on restaurant menus^[7]. Currently, there is limited insight into which environmental factors are associated with obesityinducing dietary behaviors.

Review study

In 2005 we conducted a systematic review of the literature to examine which environmental factors are consistently associated with child and adolescent energy, fat, fruit, vegetable, snack, fast food and soft drink intake^[8]. Studies published between January 1980 and December 2004 were located from four databases. The search procedure resulted in a final inclusion of 58 articles. Most of the studies were crosssectional (n=55) and environmental determinants of fruit and vegetables were studied most often (n=34). Socio-cultural and economic environmental factors were examined most extensively, especially parental intake, availability and accessibility of fruit and vegetables, and parental education. The review provided evidence for the positive association between parental intake and children’s fat and fruit and vegetable intake, for parent and sibling intakes with adolescent’s energy and fat intake, and for parent educational level with adolescent’s fruit and vegetable intake. These findings were replicated in multiple studies. The relationship between availability and accessibility of fruit and vegetables and children’s fruit and vegetable intake was less clear. A positive association was found, however the samples that found a positive association only slightly outnumbered the samples that found no association. A less consistent repeated but positive association was found for availability and accessibility on child fruit and vegetables intake.

Conclusions and implications

This review provided evidence for associations between environmental determinants and dietary intakes. However, due to important limitations of the available evidence, the results should be interpreted with caution. Most of the studies had a cross-sectional design, which makes drawing conclusions about causes and effects difficult. Another limitation is that only a few studies have been conducted on the same environmental factor – dietary behavior combination. This replication is needed to generate evidence on these associations.

In spite of the associations found in the review, there are still large gaps in the evidence regarding the influence of environmental factors on dietary behaviors. For instance very few studies on physical and political factors were retrieved. An important reason for these gaps may be that many papers on this topic might be underway, as the attention to the role of the physical environment is an emerging research field. Interventions should take the behavior of parents into account.

Parents should be strongly encouraged to give the right example, especially where fat and energy intakes are concerned. Fruit and vegetable promotion should focus especially on adolescents from parents with lower levels of education. In addition, factors such as the availability and accessibility of foods at home, school and within the neighborhood should be studied in relation to energy, fat, soft drink, snacks and fast food intake. Longitudinal studies and studies using objective assessments of the physical environment are required to gain better insight in environmental determinants of obesity-inducing behaviors.