Physical activity in children and youth in Spain: future actions for obesity prevention
L Serra-Majem, Community Nutrition Research Centre, Barcelona Science Park, University of Barcelona, C/ Baldiri Reixac 4, 08028 Barcelona, Spain. E-mail: firstname.lastname@example.org, Phone: +34-93-403-4541, Fax: +34-93-403-4543.
The aim of the study presented here was to determine the relationship between age and certain socioeconomic factors and the effect that physical activity may have on the prevalence of overweight and obesity among Spanish children and adolescents. The sample derived from the enKid study, a cross-sectional study of a representative sample of the Spanish population aged 2–24 years. Body mass index was calculated from measured weight and height. A physical activity questionnaire was administered. Age, socioeconomic level of the families, the mother's level of education, and the geographical area of residence were related to the prevalence of overweight and obesity among Spanish males.
Obesity is the consequence of an imbalance between energy expenditure, energy consumption, and energy storage in the body. Biological, behavioral, and environmental factors, such as physical activity, contribute to its etiology.1 Recent data in Spain2 reveals an alarming increase in the prevalence of obesity in children and youth, with 14% of individuals classified as obese as defined by the 97th percentile. Given that energy consumption has not increased in the recent past,3 a decrease in energy expenditure may have had some influence on the increasing prevalence of obesity.
The purpose of the study presented here was to analyze the prevalence of overweight and obesity in the Spanish population aged 2–24 years according to physical activity patterns and certain socioeconomic variables.
MATERIALS AND METHODS
The enKid study on the nutritional status and food habits of Spanish children and young people is a cross-sectional study carried out between 1998 and 2000 within a random sample of the Spanish population aged 2–24 years. The methodology of the study has been described elsewhere.4 A subsample was analyzed for compliance with the current recommendations for physical activity and included individuals between the ages of 6 and 18 years.
Dietary questionnaires and a global questionnaire incorporating questions related to socioeconomic status, educational level, and lifestyle factors (physical activity engaged in out of school, and number of hours dedicated to study, to play, to reading, to listening to music, or to practicing sports) were administered. The physical activity questions were adapted from the physical activity questionnaires used by the World Health Organization's Countrywide Integrated Noncommunicable Diseases Intervention (CINDI)5 and the Minnesota Leisure Time Physical Activity Questionnaire.6 They included questions about the type and frequency of usual sports activity at school (or at work) and out of school (months per year, days per week or month, and total hours per day), number of hours walking per day, and total number of staircases climbed per day.
Weight was measured to the nearest 0.1 kg with an electronic scale, and height was measured to the nearest 0.5 cm with a portable stadiometer (Kawe®). Body mass index (BMI) was calculated as weight/height2 (kg/m2), and overweight and obesity were defined using the following cutoff points: p85 (85th percentile) for overweight and p97 (97th percentile) for obesity, using the Orbegozo tables as the reference.7
Gender, age group, socioeconomic level (high, medium, low), mother's education level (high, medium, low), size of the population of residence, and geographical area of Spain were analyzed, along with the following physical activity variables: 1) Energy expenditure associated with physical activity at school and during leisure time. Energy expenditure was calculated as the product of the total time spent doing physical activity during leisure time and at school, multiplied by the intensity of each activity. The created variables were categorized according to the tertiles for each age group and gender. 2) An accumulation of at least 60 min of physical activity of at least moderate intensity daily.8 The sum of the time spent daily practicing sports during leisure time plus the minutes walked per day and the number of hours spent practicing sports at school were used to analyze this variable.
The fieldwork was initiated on May 1998 and ended on April 2000. Home interviews were conducted by 43 dietitians or nutritionists. For children aged 6 to 12 years, the interviews were answered by the children themselves, with support from the caretaker responsible for his/her education. Data were analyzed using the statistical package SPSS for Windows version 12.0. The chi-square statistic was calculated for comparison of proportions.
The final sample included 1443 males and 1682 females aged 2 to 24 years from the enKid study. Table 1 shows the prevalence of obesity by tertiles of energy expenditure (metabolic equivalent, or MET) at school and during leisure time, by gender, age group, and socioeconomic variables. Low energy expenditure due to physical activity at school was related to obesity among boys from 2 to 5 years of age, among boys from a high socioeconomic level (prevalence of obesity was lower in boys from high socioeconomic levels in the highest tertile of energy expenditure at school), and among boys living in cities of 50,000–300,000 inhabitants. No significant relationships were found in females. An inverse relationship between leisure time physical activity and obesity was found in males in the following groups: those aged 14–24 years, those from a high socioeconomic level, those whose mother had a higher level of education, and those who lived in big cities. No relationship was observed in females.
Table 1. Prevalence of obesity (%) according to tertiles of energy expenditure (MET) by gender, age group, and socioeconomic variables.
|Age group (years)|| || || || || || || || || || || || || || || || || || |
|Socioeconomic level|| || || || || || || || || || || || || || || || || || |
|Mother's education level|| || || || || || || || || || || || || || || || || || |
|Population size|| || || || || || || || || || || || || || || || || || |
|Region|| || || || || || || || || || || || || || || || || || |
| South and Canary Islands||252||19.5||19.0||14.3||ns||22.1||13.7||15.8||ns||282||12.5||14.9||23.0||ns||14.4||15.1||18.6||ns|
Table 2 shows the prevalence of obesity according to compliance with the recommendations for daily physical activity in individuals aged 6–18 years by gender, age, and socioeconomic variables. Among males, those complying with the recommendations for physical activity and living in populations of 50,000 to 350,000 inhabitants had a lower prevalence of obesity, as did those complying with the recommendations and living in the north of Spain. Among females from a mid-range socioeconomic level, the prevalence of obesity was lower when they complied with the recommendations for physical activity.
Table 2. Prevalence of obesity (%) according to compliance with physical activity recommendations in individuals aged 6–18 years by gender, age group, and socioeconomic variables.
|Age group (years)|| || || || || || || || |
|Socioeconomic level|| || || || || || || || |
|Mother's education level|| || || || || || || || |
|Population size|| || || || || || || || |
|Region|| || || || || || || || |
| South and Canary Islands||145||22.2||21.8||ns||160||15.3||19.4||ns|
The study of the relationship between physical activity and obesity faces several methodological problems. First, physical activity is a variable that is difficult to measure, especially in studies involving samples of a large number of individuals.9 Second, obese individuals tend to underestimate their food intake and to overestimate their physical activity patterns.10 Nevertheless, in this study, a relationship between obesity and certain variables (age, socioeconomic level, and the mother's educational level) was shown for Spanish males.
Most interventions focusing on obesity prevention in childhood include a dietary change component, a physical activity component, or a combination of both. A number of interventions focus on increasing the frequency and duration of physical exercise, while others focus on decreasing the time devoted to sedentary activity. In some cases, both aspects are targeted.11,12,13 According to the evidence from systematic literature reviews on the effectiveness of such interventions, the most successful ones do not always achieve significant changes in BMI, but they do succeed in achieving changes in dietary behavior, physical activity, or determining factors. These authors11–13 also conclude that interventions that consider the sustainability of the intervention and that establish adequate structures for this purpose are more likely to be successful. In line with this, interventions that consider the needs of schools are more often successful than those that do not.
Evidence shows that interventions aimed at promoting physical activity are more likely to be effective when they combine actions at the individual, family, school, and community levels, when they include elements for social reinforcement, and when they consider changes in policies, urban structures, and resources. Interventions that consider determinant factors that influence both engaging in or the adoption and maintenance of an active lifestyle are also more likely to be effective.14 Family support is of utmost importance for young children. According to the Spanish National Health Survey 2001, 71.7% of Spanish children and adolescents aged 6–15 years do not engage in any physical exercise in their spare time.15
At the beginning of 2005, the Spanish Ministry of Health and Consumer Affairs launched the National Strategy for Nutrition, Physical Activity and Obesity Prevention (NAOS).16 The overall strategy includes policy measures at the local level to increase resources, to expand access to safe premises, and, in particular, to encourage children to be physically active. The Ministry of Health has signed a number of agreements with companies and institutions linked to sports, and well-known athletes are collaborating in social marketing campaigns. In accordance with this, the Autonomous Government of Catalonia has launched the PAAS program (Pla Integral Per A La Promoció De La Salut Mitjançant L'Activitat Física I L'Alimentació Saludable).
A core element for the development and implementation of the NAOS strategy is a school-based intervention, the PERSEO project (Programa piloto escolar de referencia para la salud y el ejercicio, contra la obesidad), which includes a healthy-eating component and a physical activity component. This project will be evaluated in an intervention study with a group-randomized trial design involving 14,000 children aged 6–11 years and 64 schools from eight Spanish regions. The program, produced jointly by the Spanish Agency for Food Safety and Nutrition (AESAN) and the Centre for Educational Innovation and Development, is planned with a holistic school approach and encourages schools to establish School Project Committees. In addition, it examines classroom and extracurricular activities, school policy measures, school environmental changes, family support, and community reinforcement.17 These initiatives serve as examples of comprehensive evidence-based interventions to promote physical activity among the population and they constitute the first step in the battle against the increasing prevalence of physical inactivity in the society.
Declaration of interest. The authors have no relevant interests to declare.