Introduction

Obesity is a major public health concern worldwide. Over the last decade, some strategies have been implemented to decrease obesity among adolescents.¹ However, in Spain, 24.9% of boys and 17.4% of girls aged 10 to 17 years old were overweight or obese in 2011-2012.² Although scientific evidence shows higher prevalences of obesity among adolescents living in rural areas, the prevalence in urban areas is not negligible.³ Moreover, there is no consistent evidence of differences between rural and urban areas in potential obesogenic behaviours.⁴

Excess weight has been strongly associated with skipping breakfast⁵ and low physical activity (PA) levels.⁶ Additionally, although the reported relationships are not totally consistent, previous studies have also shown a positive association with higher levels of screen time⁶ and short sleep duration.⁷ Furthermore, gender differences have been found. Boys are less likely to meet food consumption and screen time guidelines and skip breakfast⁷ while girls are less likely to meet PA and sleep duration guidelines.⁸ Studies assessing the association between excess weight and multiple lifestyle risk behaviours (LRB) with a gender perspective could be relevant to address these factors in preventive programs.

This study aimed to analyse the prevalence of having multiple LRB among adolescents and the potential relationship between excess weight (including overweight and obesity) and cumulative multiple LRB among adolescents in Barcelona, Spain.

Methods

A cross-sectional study was carried out among a representative sample of 3,492 students in compulsory (year 8 [13-14 year-olds] and year 10 [15-16 year-olds]) and post-compulsory (year 12 [17-18 year-olds]) education attending secondary schools in Barcelona. Classrooms (sample unit) were randomly selected considering nine strata according to the type of school (state/private/subsidized) and the socioeconomic status (SES) of the school's neighbourhood (low/medium/high). The schools that declined to participate (n = 11) were replaced. In the study, 164 classrooms were included. Data were collected during the 2011-2012 academic year through a lifestyle risk factors survey (Factores de Riesgo en ESColares [FRESC]). The questionnaire was anonymous and self-reported.⁹ The study was approved by the Research Committee of the Public Health Agency of Barcelona.

Results

Of the 3,114 students analysed, 51.5% were girls and the mean age was 15.9 years. In compulsory schooling, the prevalence of excess weight (including overweight and obesity) was 32.4% in boys and 23.0% in girls (p <0.001). In the post-compulsory schooling, 23.7% of boys and 15.1% of girls were overweight (p = 0.001) (Table 1).

Table 1 Distribution of lifestyle risk behaviours and weight status among secondary school students (13-19 years-old) by grade and sex. FRESC Survey^a 2012, Barcelona (Spain). 

^aFRESC Survey [Factores de Riesgo en ESColares (Risk Factors in Schoolchildren)].

^bp value for the chi-squared test.

^cMissing values <0.5%.

^dAge- and sex-specific body mass index z-score cut-offs defined by the World Health Organization.

^eWatching television, playing videogames or using the computer for leisure purposes ≥2 h/day.

^fLifestyle risk behaviours considered: exceeding screen time recommendations (≥2 h/day), skipping breakfast at least once a week, not following physical activity recommendations (<1 h/day) and not sleeping the recommended amount of time (<8 h/day).

Less than 2% of students had no one LRB. 80.4% of boys and 85.4% of girls in compulsory schooling (p = 0.002) and 94% of students in post-compulsory schooling had ≥2 LRB. The prevalence of 4 LRB in compulsory schooling was 10.4% in boys and 17% in girls (p <0.001). In post-compulsory schooling, these percentages were 23.2% and 29.0%, respectively (Table 1).

In compulsory schooling, the aPR of excess weight increased with the number of LRB reported. The highest probability of excess weight was found among students with 4 LRB (aPR = 1.56; 95% confidence interval:1.19-2.05) (Table 2).

Table 2 Prevalence of overweight (refers to overweight and obesity) according to lifestyle risk behaviours and association between excess weight^a and multiple lifestyle risk behaviours among secondary school students by grade. FRESC Survey^b 2012, Barcelona (Spain). 

aPR: adjusted prevalence ratio; 95%CI: 95% confidence interval.

^aUnderweight and normal weight were considered as the reference group.

^bFRESC Survey [Factores de Riesgo en ESColares (Risk factors in schoolchildren)].

^cIndependent models adjusted by sex, age, family affluence scale, type of school and socioeconomic status of school's neighbourhood.

^dWatching television, playing videogames or using the computer for leisure purposes ≥2 h/day.

^eLifestyle risk behaviours considered: exceeding screen time recommendations (≥2 h/day), skipping breakfast at least once a week, not following physical activity recommendations (<1 h/day) and not sleeping the recommended amount of time (<8 h/day).

Discussion

This study shows that more than 80% of students have multiple LRB, observing a higher prevalence of multiple LRB in girls. Additionally, excess weight is positively associated with a higher number of LRB among students in compulsory schooling.

In general, adolescents fail to meet health-behaviour guidelines. More than 50% of Swiss adolescents do not meet health-behaviour guidelines when considering screen time, PA and diet.¹² Likewise, nearly 80% of the US adolescents have multiple dietary and PA risk behaviours.¹³ Similarly, we found that more than 80% of the adolescents were involved in ≥2 LRB. Additionally, among the compulsory schooling students, we found a higher prevalence of multiple LRB in girls. Although the Swiss study¹² did not show gender differences, other published studies^13,14 are in line with the gender differences observed in our study.

PA and short sleep duration were not associated with excess weight. The PA reported by the students referred to exercise that implied physical effort. Accordingly, not all the sources of PA were assessed, such as walking to/from school, which has been related to excess weight.¹⁵ This underestimation of PA could partly explain the lack of association.

In compulsory education, we found that the prevalence of being excess weight was more than 32% higher among adolescents who reported ≥1 LRB. This percentage rose to 56% in adolescents reporting 4 LRB. The analysis conducted for boys and girls separately showed similar aPR for both sexes. Similarly to our results, a US study showed that adolescents with a higher number of LRB were more likely to be overweight, when analysing watching television, PA and fruit/vegetable intake.¹³ Finally, a study performed among Spanish adolescents¹⁴ found that the combination of not meeting the recommendations for PA, television watching, sleep duration and meal frequency was associated with higher levels of body fat and excess weight.

This study has some limitations. First, LRB data were self-reported, which could lead to an information bias. However, anonymous questionnaires were used to minimize this bias. Second, there was a high percentage of missing data (10%) when the variable multiple LRB was built. However, no differences were found between included and excluded students. A strength of this study is that it has been performed in a representative sample of in-school adolescents in an urban European context. Moreover, weight status was defined from objective measures, which guarantees the validity of the dependent variable.

The high prevalence of adolescents with multiple LRB should be considered to tackle obesity. The results obtained highlight the importance of considering a multiple-behaviours approach in school-based preventive programs focused on controlling excess weight in adolescents.