Introduction

Children develop their eating habits and food preferences as they grow (Birch & Fisher, 1998). Many different factors influence food habits in a complex interactive way. Parents and the family environment are very important for young children to learn and develop food preferences and eating habits in a dual way (Story et al, 2002). On the one hand as providers of the food children eat, family members are also relevant role models and establish rules and norms related to food and eating practices. As children grow and start school, teachers, peers and other people at school together with the media and social leaders become more important. Progressively children are more independent and start making their own food choices. The peer group is key for adolescents and has a major influence in developing food habits and lifestyles (Cusatis & Shannon, 1996).

Different models and theories have been suggested to explain interactions among influencing factors on food habits (Story et al, 2002). Availability and access to a variety of foods have been identified as key elements in this context together with psychological processes at individual and social levels and other factors that influence food choices. However, availability and access to food are influenced by a number of other situations; among them socioeconomical aspects and prevailing lifestyles (Roos et al, 1998).

This paper examines the influence of socioeconomical determinants and lifestyles on usual food patterns of Spanish children and young people.

Methods

The enKid study is a population-based cross-sectional study carried out on a random sample of the Spanish population aged 2–24 y (n=3534; 1629 boys and 1905 girls). The sample was drafted by a multiple step sampling procedure based on the population census. Sampling and response rate have been described elsewhere (Serra-Majem & Aranceta, 2000).

The study protocol included socioeconomical family background (level of education of the mother and the father classified as low, medium, high; occupation of mother and father). Dietary intake was assessed by means of a 24-h recall (child with the mother or person responsible for the child's feeding for children under 8 y) and a second 24-h recall in 25–30% of the sample. Additionally, a 164 item food frequency questionnaire was completed for each participant along questions on dietary habits; consumption of supplements; physical activity on weekdays as well as leisure time; tobacco and alcohol use; food preferences and a questionnaire on basic information regarding food and nutrition (Serra-Majem, Aranceta et al, 2002). Anthropometrical measurements were assessed on each individual following standard protocols (Serra-Majem, Ribas et al, 2002). All questionnaires were specially designed for the study and were previously pretested and validated.

Data were collected by trained dietitians during a personal interview with each participant and their mother or person responsible for feeding the child for those under 8 y.

The study protocol was approved by the ethical committee of the Spanish Society of Community Nutrition. Parent consent was requested for each participant. All field workers followed a training period prior to data collection. Field work was completed between May 1998 and April 2000.

In this paper, the influence of socioeconomic factors, overweight and physical activity on usual food patterns estimated by the food frequency questionnaire is analysed. Inadequate consumption by food group was calculated by comparison to Spanish dietary recommendations. Prevalence of inadequate consumption across groups was compared by ² statistic for rates and proportions. Factor analysis by the principal components method and varimax rotation was run on z-scored transformed food consumption variables in order to identify salient food patterns in the group. Multiple linear regression models were fitted following a stepwise forward method to assess the relationship between selected factors, sociodemiographic and lifestyles variables on two different levels; firstly sociodemographic factors (age, gender, parental education and occupation, geographical region and rural–urban distribution) as background variables and then lifestyle factors (leisure time physical activity, sport practices, overweight). Tolerance for entering the model was fixed at a probability value for F statistic <0.05. Separate models were fitted for children under 14 y of age and for adolescents and young people aged 14–24 y. Data analysis was performed using SPSS v 10.

Results

Overall response rate to the survey was 68%. Table 1 shows sociodemographic characteristics of the study sample and prevalence of inadequate consumption for dairy products, fruit and vegetables across categories.

Table 1 - Distribution of the study sample and prevalence of inadequate consumption of dairy products, fruit and vegetables by selected sociodemographic characteristics and lifestyle factors.

Full table

Average consumption of vegetables was low. The highest proportion of inadequate intake for this food group (<2 portion/day) was observed among 10–13 y-old boys and 6–9 y-old girls (²=55.3; P<0.001). Higher proportions of inadequacy were observed among children living in small towns compared to urban areas or small localities (²=34.3, P<0.001 boys; ²=13.9 P<0.05 girls) and children living in the northern and southern regions of the country as well as those living in the Canary islands (²=77.9, P<0.001 boys; ²=116.9, P<0.001 girls).

Girls aged 14 y and older, and boys 18 y and older showed the highest proportions of adequate consumption for the fruit group (3 portions/day) according to Spanish recommendations, although differences were not significant. Children and young people living in big cities showed the highest proportions of inadequate intake for fruit (²=34.7, P<0.001, boys; ²=18.46, P<0.01 girls).

The youngest age group (2–5 y) showed the lowest proportions of inadequacy for the dairy group (P<0.001; ²=39.11 boys; ²=49.60 girls).

Factor analysis identified five main components of dietary patterns labelled 'Snacky', 'Healthy', 'Protein rich', 'Meat rich' and 'Ludicrous', which explained 58.9% of the variance. Food groups factor loading and percent of variance explained by each factor are shown in Table 2.

Table 2 - Dietary patterns identified by principal components and varimax rotation factor analysis. Food groups factor loadings.

Full table

The 'Snacky' pattern was characterised by more frequent and higher consumption of bakery products (buns, cakes and biscuits), sweets, salted snacks and soft drinks. Higher intakes of fruit, vegetables and fish were associated to the 'Healthy' pattern. The 'protein-rich' pattern was characterised by a high consumption of pulses, eggs, dairy products and cereals. The 'Ludicrous' pattern was characterised by the consumption of alcoholic beverages and soft drinks.

Table 3 shows regression coefficients estimated in the models fitted for the 'Healthy' and 'Snacky' patterns for children under 14 y and for adolescents and young people aged 14–24 y. The 'Snacky' pattern showed a positive association with age among children under 14 y, but negative among adolescents and young people. Level of education of the mother was inversely associated in both the age groups. Children and young people who watched television more than 2 h daily were more likely to follow this pattern. Gender could not enter in either models. Age entered in the regression models fitted for the 'Healthy' pattern among children and people aged 14–24 y. Increasing age was more important for the younger group. Girls were more likely to follow this pattern in both the age groups, while children and young people whose mother had achieved a lower level of education were less likely. Among children, time spent watching television showed a negative association with the 'Healthy' pattern.

Table 3 - Regression coefficients in predictive models for the 'healthy' and 'snacky' dietary patterns in children 2 –13 y and people aged 14-24 y.

Full table

Discussion

The enKid study has contributed relevant cross-sectional data on nutrition, lifestyles and health on Spanish children and young people. Owing to the sample design, sampling methods and response rate, the enKid results can be considered representative of the Spanish population aged 2–24 y. The study protocol was carefully designed, pretested and validated prior to data collection (Serra-Majem & Aranceta, 2000, 2001).

According to the results of the enKid study, children and young people from a lower socioeconomic background and those whose mothers had a lower level of education showed a higher consumption of sweets and high-fat bakery products as well as sugary and salted snacks, but lower vegetables intake. Similar patterns have been described in other studies in US children and adolescents (Nicklas, 1995; Lowry et al, 1996; Neumark-Sztainer et al, 1996; Munoz et al, 1997; Zive et al, 1998), in the School Health Promotion Survey carried out in 76 201 Finnish Secondary school students in 1997–1998 (Roos et al, 2001) and other European studies (Lien et al, 2002).

Several studies carried out in the USA suggest that sugary soft drinks are replacing milk in the diet of children and adolescents (Neumark-Sztainer et al., 1997; Lytle, 2002). The enKid study shows that 45.7% of 14–17 y old girls had inadequate consumption for the dairy group.

Factor analysis is a useful technique to summarise food patterns and relate them to different socioeconomical and lifestyle factors. However, it must be acknowledged the method is data-specific, thus the pattern and their associations extracted in one study population may not be reproduced in other populations (Schulze et al, 2003). This kind of analysis can facilitate the development of interventions aimed at modifying eating patterns, rather than specific components of the diet (Mishra et al, 2002).

According to the results of factor analysis, the 'meat-rich' pattern contributes to a higher proportion of the variance in the model (22.48%), followed by the 'Snacky' and 'Healthy' patterns. Regression models fitted for the last two could not explain the high proportion of variance in the patterns. However, both cases contributed to identifying useful predictors in this population, which are valuable to design interventions. This fact is particularly relevant, since there is some evidence suggesting that food habits and lifestyles that persist during adolescence are more likely to track into adulthood (Klepp, 1994).

The CARDIAC study in the USA showed that children who often consumed fatty snacks or had their evening meal away from home had higher intakes of total fat and saturated fats, thus showing a higher risk dietary profile (Gonzales et al, 2002).

Other studies have described an association between a higher level of physical activity and adherence to healthier dietary pattern. A recent study in a sample of young people in Navarra (Spain) reported an association between a higher level of physical activity during leisure time and adherence to a food pattern identified as the 'Spanish-Mediterranean' diet. Conversely, young single males with a sedentary lifestyle were more likely to follow a Western dietary pattern (Sanchez-Villegas et al, 2003). In the enKid study, children and young people who usually spend longer watching TV were more likely to follow the 'Snacky' pattern, characterised by higher intakes of bakery products, sweets and salted snacks. A number of studies suggest that a sedentary lifestyle is associated with higher consumption of salted and sugary snacks as well as soft drinks (Serra-Majem & Aranceta, 2001; Lowry et al, 2002; Lytle, 2002).

Lower education and socioeconomical family background is associated with less healthier dietary patterns. Other studies point these population groups as higher risk for overweight both for children and adults in the family (Serra-Majem & Aranceta, 2001). Results from this study highlight the importance of enhancing school-based and community-based actions to promote healthy eating and physical activity addressed to children and young people (Aranceta, 2001). Specific actions involving families and increased opportunities to easier healthy food choices will be required.

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