Obesity is a chronic disease of a multifactorial origin. Both genetic and environmental factors are involved in its development. It appears as an alteration of body composition with an increase in the fat compartment. This increase in the deposits of adipose tissue, in most cases, goes together with an increment of body weight and a considerable increase in the risk of comorbidities that affect the quality and life expectancyReference Calle, Thun, Petrelli, Rodriguez and Heath1–Reference Roth, Qiang, Marba’n, Redelt and Lowell4.
Evidence shows that a clear environmental component is involved in the development in 95% of the cases of obesity, linked to a sedentary lifestyle and dietary habits that favour a positive energy balance and, as a consequence, a gradual deposit of fat massReference Swinburn, Caterson, Seidell and James5.
The International Obesity Task Force (IOTF) and the World Health Organization (WHO) have qualified obesity as the epidemic of the 21st century for the dimensions acquired, the impact on morbidity/mortality, quality of life and health costs6. The problem is not restricted to industrialised societies; developing countries and particularly those undergoing transition situations experience the same, often coexisting with malnutrition. Of special concern is the increasing numbers of overweight children and adolescents in many countriesReference Martorell, Caballero and Popkin7. Major environmental and lifestyle changes related to diet and physical activity have been implicated in the increasing trends of overweight6.
The WHO report on diet and health recognises the impact of obesity in the development of the most prevailing chronic diseases, namely type 2 diabetes, cardiovascular diseases, muscle–skeletal pathology and several types of cancer8.
The increase in body volume also causes dysfunctions of body image, self-esteem and in the interaction with the environment, thus generating important economic, direct and indirect costs, as well as an important health and social demand (clinical consultation, work absenteeism, disability, special care needs, etc.)6.
The prevalence of obesity in Spain
Prevalence of obesity in Spain has been estimated on the basis of individual measurements of body weight and height on countrywide random population samplesReference Aranceta Bartrina, Serra-Majem, Foz Sala and Moreno Esteban9.
Current data show a prevalence of obesity (body mass index (BMI) ≥ 30 kg m−2) in the Spanish adult population aged 25–60 years of 15.5% (13.2% in men and 17.5% in women)Reference Aranceta, Pérez Rodrigo, Foz Sala, Mantilla, Serra Majem and Moreno10. In this age group, the prevalence of obesity increases with age, is significantly higher in women than in men and is inversely related with the educational level and socio-economical situationReference Aranceta, Pérez-Rodrigo, Serra-Majem, Ribas, Quiles-Izquierdo and Vioque11. Women 45 years and older with a low educational level are the subgroup showing the highest prevalence of obesity.
There are statistically significant differences in the distribution of BMI by region, both in men and women. In the female subgroup, the prevalence of obesity is higher in the northwest (21.8%), south (23%) and the Canary Islands (22.2%) compared to the North-East and Central (14.3%) regions of the peninsula. The regional distribution of obesity across the country in the male subgroup follows a similar pattern, with higher rates in the South (19.9%) and Northwestern (19%) region compared to the North-East (8.9%).
In the population older than 60 years, the estimated prevalence of obesity is 35%: 30.9% in men and 39.8% in womenReference Aranceta Bartrina, Pérez Rodrigo, Muñoz Hornillos, Muñoz, Aranceta and Guijarro12, Reference Gutierrez-Fisac, López, Banegas, Graciani and Rodríguez-Artalejo13.
Results from the enKid study – a cross-sectional survey performed between 1998 and 2000 on a random sample of the Spanish population aged 2–24 years including measured body weight and heightReference Serra-Majem, Ribas Barba, Aranceta Bartrina, Pérez Rodrigo, Saavedra Santana and Peña Quintana14 – estimate a prevalence of obesity in this age group of 13.9%, 12.4% for overweight. Cutoffs were defined based on BMI, considering the 85th percentile for overweight and the 97th percentile for obesity of the Spanish reference distribution and growth charts15. Overall, overweight and obesity account for 26.3%. Obesity is higher in the male subgroup (15.6%) compared to females (12.0%). Among boys, prevalence rates were highest between 6 and 13 years. In the female subgroup prevalence rates were highest between 18 and 24 yearsReference Serra-Majem, Ribas Barba, Aranceta Bartrina, Pérez Rodrigo, Saavedra Santana and Peña Quintana14.
Logistic regression analysis of sociodemographic determinants of obesity in the enKid study showed that low education level of the mother, low socio-economic family background and living in the South of the country or in the Canary Islands increased the likelihood of being obeseReference Serra-Majem, Aranceta-Bartrina, Perez-Rodrigo, Ribas Barba and Delgado16.
Regarding lifestyle factors, breastfeeding for at least 3 months had a protective effect in young children together with the consumption of ≥4 portions fruit and vegetables everyday, and a dietary pattern providing <35% energy from fat and being physically active, that is practice a sport activity regularly ≥2 days per week. Conversely, high consumption of cakes and buns, softdrinks and butchery products, a dietary pattern with ≥38% energy from fat and low physical activity levels, including spending ≥3 hours per day watching TV, increased the likelihood of being obese (Table 1).
Table 1 Predictors of obesity in Spanish children and young population aged 2–14-year-old in the enKid study. Odds ratio of prevalence of obesity
* Fitted for children under 6 years of age.
Low physical activity has been directly related to a higher prevalence of obesityReference Bar-Or, Foreyt, Bouchard, Brownell, Dietz and Ravussin17. In the last decades, the urbanisation process in western societies has been associated with lower energy output at work, in household tasks and increased use of public transportation, cars and lifts, among other factors18. Children games and other leisure time activities are often sedentary, such as watching TV or computer games. On the other hand, outdoor playing opportunities are limited and time devoted to physical activity in the school curriculum has decreased. In recent years, many studies have reported a positive association between the number of hours watching TV daily and the prevalence of overweight in childrenReference Gortmaker, Must, Sobel, Peterson, Colditz and Dietz19.
In recent decades, some countries have experienced a decrease in total fat intake, but at the same time there is a clear increase in energy density in the food model due to lower consumption of fruit, vegetables and pulsesReference Lobstein, Baur and Uauy20.
In this stage of life, overweight is not associated with higher mortality rates in the short term, but with increased risk in adult life. However, childhood obesity has an impact on the child’s quality of life, favours a low self-esteem and poses a risk of discrimination and stigmatisationReference Dietz21, Reference Reilly, Methven, McDowell, Hacking, Alexander and Stewart22. Long-term follow-up studies in children and adolescents show that the likelihood of being obese in adulthood is two-fold in obese children compared to the non-obese, particularly among those considerably overweight and those who remain overweight over adolescenceReference Freedman, Khan, Serdula, Dietz, Srinvasan and Berenson23, Reference Whitaker, Wright, Pepe, Seidel and Dietz24.
Prevention of overweight
Public Health strategies and the improvement in technologies and therapeutic procedures have contributed to a considerable reduction in mortality due to cardiovascular diseases over the last years. However, this trend can change unless the continuing increase in obesity, an independent risk factor for these processes, is reversed.
The development and implementation of obesity prevention strategies require the identification and understanding of determinant factors, particularly the environmental factors that can be influenced when addressed by effective action plans on a large scale over time.
There is a growing number of studies investigating the influence of environmental factors on obesity-related behaviours, such as dietary practices and physical activity in children and adolescentsReference Swinburn, Caterson, Seidell and James5, 25. Different frameworks and classifications have been suggested to order the complexity of potential environmental influencesReference Swinburn, Egger and Raza26.
Effective weight management for individuals and groups at risk of developing obesity involves a range of long-term strategies: prevention, weight maintenance, management of co-morbidities and weight loss. They should be part of an integrated, multisectoral, population-based approach, which includes environmental support for healthy diets and regular physical activityReference Swinburn, Caterson, Seidell and James5–Reference Martorell, Caballero and Popkin7.
Systematic reviews of effectiveness of intervention programmes highlight the difficulty of comparing results obtained in different intervention studies. Early literature reviews on effectiveness of school-based nutrition education programmes identified educational strategies directly relevant to a behavioural focus and theory driven among the elements conducive to successful programmesReference Contento27. Other features that contribute to gain effectiveness are the provision of adequate time and intensity for the intervention, involvement of families, particularly for younger children and incorporation of self-assessment and feedback in interventions for older children. Interventions that include actions to modify the school environment and those that involve the larger community are more likely to be effectiveReference Contento27.
A number of authors have systematically reviewed the evidence of interventions aimed at preventing child obesityReference Summerbell, Waters, Edmunds, Brown and Campbell28–Reference Doak, Visscher, Renders and Seidell30. The conclusions of these reviews have been consistent, in part due to the limited number of high-quality, medium-long term, randomised controlled trials. A recent review by Doak et al.Reference Doak, Visscher, Renders and Seidell30 gave rise to some controversies. More of the non-effective studies in this review intervened both on diet and physical activity, included physical activity outside school as part of the intervention and targeted the physical environment as a strategy to increase access to healthy lifestyles for the intervention group. Furthermore, the non-effective interventions scored higher on sustainability of the programme. These findings highlight the difficulties in quantitative comparisons of school-based intervention studies. The quantitative comparisons in effectiveness reviews only consider whether a specific component has been included in the intervention or not, but do not take into account how this component was designed, how it was addressed or to what extent it was implementedReference Doak, Visscher, Renders and Seidell30. Difficulties in randomisation and control in complex community intervention trials, which happen in an everyday life context, have been argued and different approaches to overcome them have been suggestedReference Hawe, Shiell and Riley31.
All interventions that aimed to reduce television viewing as part of the intervention by different means, such as the Planet Health programReference O’Dea32, were successful. It should be noticed that all these studies were conducted in the USA, where children spend more time viewing television, the number of television sets at home is higher and more advertisements are shown on television compared to other countries.
The contribution of family support and parental involvement to the effectiveness of interventions is not clear from this review. However, systematic reviews that addressed the environmental determinants of obesity-related dietary behaviours concluded that the family environment, including parental intake of fat and soft drinks, parental intake of fruit and vegetables, modelling behaviours, parenting styles, parental educational level as well as availability and access to fruit and vegetables at home, are relevant factors influencing children and adolescent eating practices25. Thus, interventions should consider parents behaviour. The evidence regarding the influence of physical, sociocultural, economic and cultural factors in the school is limited.
Only a few studies assessed the potential for unhealthy outcomes, such as the impact on being underweight or overweightReference O’Dea32. Of particular importance would be to assess the effect of obesity prevention programmes on underweight children, either by showing the frequency distribution for the outcome measures or by presenting results separately for overweight, normal and underweight childrenReference Caballero, Clay, Davis, Ethelbah, Rock and Lohman33. The goal for primary prevention programmes would be to maintain a normal distribution of BMI in the intervention group. To achieve this, the intervention should be targeted to modify obesity-related behaviours without contributing to weight loss in other healthy childrenReference Doak, Visscher, Renders and Seidell30. In the review conducted by Doak et al.Reference Gortmaker, Peterson, Wiecha, Sobol, Dixit and Fox34, only the ‘Planet Health’ study assessed separately eating disorders, showing a beneficial effect.
The ‘Know your Body’ study focused on the potential stigmatisation of overweight children due to the interventionReference Resnicow, Cross and Wynder35. Particular care should be placed when formulating messages and during the implementation of the program not to contribute to the emotional and mental distress of children who are already overweight or obeseReference O’Dea32.
Outcome measures in the evaluation of interventions that include a physical activity component cannot be assessed only by BMI because of an increase in lean body mass. It should include appropriate indicators of body fatness according to age, sex and ethnicity of the groupReference Doak, Visscher, Renders and Seidell30, Reference Caballero, Clay, Davis, Ethelbah, Rock and Lohman33.
Among the difficulties reported for the sustainability of the interventions in intervention studies were limited time in the school curriculum, burden of the teachers or even concern of parents, teachers and school staff about a negative impact on the academic performance of children due to the extra burden of the interventionReference Doak, Visscher, Renders and Seidell30, Reference Yager and O’Dea36, Reference Sahota, Rudolf, Dixey, Hill, Barth and Cade37.
There is sound evidence that positive changes in food habits and physical activity could contribute to prevent the problem38. On this basis, the WHO approved in the 57th World Health Assembly in 2004 the Global Strategy on Diet and Physical Activity encouraging all member states to develop and implement national action plans39.
The SEEDO 2000 Consensus also emphasised the need to develop and implement strategies for the prevention of obesity in Spain40. A joint document issued in 2003 by the Spanish Society of Community Nutrition (SENC), the Spanish Association of Paediatrics (AEP) and the Spanish Society for the Study of Obesity (SEEDO) identified a list of recommendations for the prevention of obesity in children and young peopleReference Serra Majem, Aranceta Bartrina and Rodríguez-Santos41. The important role of the family and the school setting as well as the responsibility of the Health Administration and Paediatric care in the prevention of obesity was highlighted in the document.
In line with these, the Spanish Ministry of Health along the Spanish Agency of Food Safety and Nutrition encouraged the development of the NAOS strategy, a National Action Plan for Nutrition, Physical Activity and Obesity Prevention, as the result of the contributions of eight multidisciplinary working groupsReference Neira and de Onis42. The strategy comprises a number of actions involving stakeholders in different sectors, policy measures and regulations pursuing a favourable environment. As part of the strategy, the PERSEO project is a multicomponent school-based intervention targeted to foster healthful dietary habits, decrease sedentary behaviours and increase physical activity among 6–10-year-old children. The intervention includes a school curriculum, changes in the school environment and a family component.
Obesity prevention must begin from early stages of life. In this sense, it is important to ensure an adequate nutritional status during pregnancy, not only for the benefit of the mother’s health but also for the future of the newborn baby. Evidence of foetal programming has been emphasised in recent years. Nutritional factors in utero life, around birth and early life have been associated with the development of risk factors and chronic disease in adulthood, such as type 2 diabetes and obesity, especially in underweight newborn babiesReference Remacle, Bieswal and Reusens43.
Diet is the main exogenous factor that influences children’s growth and development. On the other hand, as children grow, they acquire dietary habits and lifestyles that will have an influence on his diet as an adult. Longitudinal studies in cohorts of children and youths are not conclusive regarding the tracking of dietary habitsReference Mikkila, Rasanen, Raitakari, Pietinen and Viikari44, Reference Kvaavik, Andersen and Klepp45. It seems clear that it is easier to promote healthy eating practices and lifestyles during childhood than to change already structured habits in adulthood. Therefore, diet during the first year of life and along the whole childhood, school age and adolescence play a very important part in health prevention and promotionReference Darnton-Hill, Nishida and James46.
Public Health experts, academics and politicians agree that there is a need for action to prevent obesity. Evidence show that prevention is potentially more efficient than treatment alone against obesity47. The controversy arises regarding what preventive measures should be taken and who are the target groups. More recently, the debate has focused on the avoidance of the blaming and stigmatisation of the obese, and furthermore, on how to avoid unwanted harmful effects while taking action against obesity at the population level.
Population strategies aimed at the primary prevention of obesity should be multifaceted, actively involve stakeholders and major actors concerned and consider multiple settings for implementation. They should consider the promotion of healthy eating practices, which include adequate amounts of fruit and vegetables, enhancement regular practice of physical activity and a reduction of sedentary behaviours in order to avoid weight gain and maintain body weight in the healthy rangeReference Doak, Visscher, Renders and Seidell30.
Particular care should be placed when formulating messages to avoid unwanted harmful effects and to tailor them according to the characteristics and needs of the target populationReference Doak, Visscher, Renders and Seidell30, Reference O’Dea32. Such action plans should consider components that directly influence the environment in order to make the healthier choice available and accessible to the population. Of special relevance is the quality and variety of food and drinks available or offered in schools, either as part of school meal programmes or as any other means and outlets18, Reference Sahota, Rudolf, Dixey, Hill, Barth and Cade37, 39, Reference Serra Majem, Aranceta Bartrina and Rodríguez-Santos41, Reference Story48.
Interventions that are incorporated into the school curriculum are more likely to be sustainable over time, thus being more likely to be effectiveReference Doak, Visscher, Renders and Seidell30, Reference Sahota, Rudolf, Dixey, Hill, Barth and Cade37. Figure 1 summarises a number of actions to consider in community-based interventions for the prevention of obesity.
Fig. 1 Obesity prevention strategies: elements and actions to be considered
Overall institutional support by means of health and nutrition policies, including the regulation of food marketing strategies, the quality of foods and drinks available in schools39, Reference Hawkes49, and the provision of adequate resources devoted to school-based nutrition education and physical activity engaging actions are required for effective actions.
Acknowledgements
Conflict of interest: None of the authors had any conflicts of interest in connection with this study.
Authorship responsibilities: J.A. was lead author, provided the concept and design for this paper. He also provided main data sources for this review. He directed some of the studies mentioned in this paper. He also contributed to the writing of this manuscript. C.P.R. contributed to the writing and editing of this paper, revised the manuscript providing expert advice on data interpretation and discussion. L.S.M. provided main data sources for this review. He directed some of the studies mentioned in this paper. He also revised the manuscript providing expert advice on data interpretation and discussion. D.B., M.L.T., X.F. and B.M. revised the manuscript providing expert advice.
Guarantor: Javier Aranceta.
