International Journal of Epidemiology, 2014, 675–678 doi: 10.1093/ije/dyu095 Advance Access Publication Date: 28 April 2014
COCHRANE COLUMN Taryn Young, Charles S Wiysonge1
This column highlights Cochrane Reviews relevant to public health to stimulate debate about the review findings, their application, or methodological aspects that the reviews raise. In this issue, we look at a review summarizing interventions to prevent obesity in children. Anel Schoonees from South Africa summarised the Cochrane Review conducted by Walters and colleagues; and Maylene Shung King from South Africa, and Ricardo Uauy and Juliana Kain from Chile have written commentaries.
1
Centre for Evidence-based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa. E-mail: [email protected]. Website: www.sun.ac.za/cebhc
Anel Schoonees Centre for Evidence-based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa. E-mail: [email protected] summarized this Cochrane Review.
Background More and more children worldwide are overweight or obese, increasing their risk of medical problems including non-communicable diseases, and psychosocial problems including self-esteem, depression and bullying. A team from Australia, the United Kingdom and Hong Kong reviewed trials that evaluated interventions promoting healthier diets and increased physical activity to prevent children from becoming overweight and obese.
Methods The last search for the Cochrane Review was conducted in March 2010. Randomised and non-randomised controlled trials of at least 12 weeks duration that compared interventions targeting dietary behaviour, physical activity, or both with no intervention or a different intervention in children aged from 0 to 18 years old were included. Body mass index (BMI) was the main outcome.
Results Fifty-five studies were included, 50 in high-income countries, mostly North America. Thirty-nine studies included children aged between 6 and 12 years and 41 studies ranged between 12 and 52 weeks. The most common
setting for interventions was schools in 43 studies. The meta-analysis included 37 studies (27 946 children). A funnel plot suggested that some small studies that did not demonstrate an effect may not have been published, potentially influencing the meta-analysis. Table 1 shows the review’s main findings, including quantification of the effect size and consistency of findings. The review authors did not assess quality of the evidence with GRADE.
Conclusion Short-term obesity prevention interventions for children can be effective if carefully and thoroughly planned, implemented, monitored and regularly evaluated. Trials with long-term follow-up are needed. It remains unclear which specific dietary (such as a focus on increasing vegetable and fruit intake) or which physical activity (such as mandatory participation in school sport) components are the most effective. The full text of the review is available in The Cochrane Library: Waters E, de Silva-Sanigorski A, Hall BJ, Brown T, Campbell KJ, Gao Y, Armstrong R, Prosser L, Summerbell CD. Interventions for preventing obesity in children. Cochrane Database of Systematic Reviews 2011, Issue 12. Art. No.: CD001871. DOI: 10.1002/14651858. CD001871.pub3.
675
Downloaded from http://ije.oxfordjournals.org/ at New York University on May 15, 2015
Interventions for preventing obesity in children
676
International Journal of Epidemiology, 2014, Vol. 43, No. 3
Table 1. Effects of interventions on body mass index (kg/m2) Study characteristics
Subgroup
Number of trials
Number of children
Standardised mean difference
Heterogeneity (I2)
(95% confidence interval)* Type of intervention
Age
Study setting
Risk of bias
16 6 27
9245 2793 15 908
0.11 0.12 0.18
( 0.19 to 0.02) ( 0.28 to 0.05) ( 0.27 to 0.09)
66% 76% 82%
8 31 10 35 6 8 35 14 21 22 6
1815 18 983 7148 22 904 4086 956 17 003 10 943 5369 16 576 6001
0.26 0.15 0.09 0.14 0.09 0.28 0.17 0.12 0.16 0.14 0.16
( ( ( ( ( ( ( ( ( ( (
85% 79% 79% 79% 56% 87% 80% 79% 68% 85% 74%
0.53 to 0.00) 0.23 to 0.08) 0.20 to 0.03) 0.21 to 0.08) 0.20 to 0.02) 0.72 to 0.16) 0.25 to 0.09) 0.21 to 0.03) 0.27 to 0.05) 0.23 to 0.05) 0.27 to 0.04)
*Effect sizes shown are for combined physical activity and dietary interventions, unless otherwise stated.
Commentary: Childhood obesity: A growing dilemma for public health interventions and research alike Maylene Shung King Health Economics Unit, School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa. Email: [email protected]
Childhood obesity is a growing public health problem that cuts across country, socio-economic, and cultural contexts. It has implications for the immediate health of children, as well as being a pre-cursor for non-communicable diseases in adulthood. A recent South African review article showed that the prevalence of overweight and obesity in primary school children has increased more than ten-fold in ten years.1 This is mirrored on the wider African continent where, despite persistent hunger and under-nutrition, overweight and obesity in children is estimated to have doubled in recent years.2,3 Roussouw et al describe the unhappy coexistence of a dual burden of disease: “…undernutrition and overweight or obesity are found in the same populations, in the same households, and even in the same children.” This reflects the complexity that overweight and obesity presents, and implies that interventions to address these phenomena must consider this complexity.
The Cochrane Review outlines the state of play of intervention programmes to reduce and avert childhood obesity. It showcases the growing attention given to childhood obesity in high-income countries, while highlighting the paucity of published intervention research from low and middle-income countries – an indicator suggesting that childhood obesity as a public health problem is still eclipsed by other priority health problems. The review appropriately groups studies according to interventions by age groups and thus highlights the unsurprising emphasises on primary school children. A World Bank review of school health services globally corroborates that nutrition is a key focus in school health programmes.2 The review highlights challenges and opportunities. The great variety of interventions, and the variable contexts in which they are applied, presents a challenge for the metaanalysis, as well as for the conclusions that may be drawn
Downloaded from http://ije.oxfordjournals.org/ at New York University on May 15, 2015
Duration of interventions
Physical activity interventions Dietary interventions Combined physical activity and dietary interventions Age 0 to 5 years Age 6 to 12 years Age 13 to 18 years Education setting only Education and other settings Non-education setting Duration 12 months Duration > 12 months Low risk of bias Unclear risk of bias High risk of bias
International Journal of Epidemiology, 2014, Vol. 43, No. 3
lifespan. Lastly, the answer to childhood obesity, as with many health problems, may not reside with specific narrow interventions, but is probably best addressed ‘up-stream’, where key determinants of health are located. In this instance part of the answer may lie in targeting the food and beverage industry to reduce the production of the numerous unhealthy products that put children and their families at risk of poor health and disease.3
References 1. Rossouw HA, Grant CC, Viljoen M. Overweight and obesity in children and adolescents: The South African problem. S Afr J Sci. 2012;108. 2. De Onis M, Blo¨ssner M, Borghi E. Global prevalence and trends of overweight and obesity among preschool children. Am J Clin Nutr. 2010;92:1257–1264. 3. De Onis M, Blo¨ssner M. Prevalence and trends of overweight among preschool children in developing countries. Am J Clin Nutr. 2000;72:1032–1039.
Commentary: Interventions for preventing obesity in children (Review) Ricardo Uauy and Juliana Kain Institute of Food Technology and Nutrition (INTA), University of Chile, Chile. E-mail: [email protected]
Obesity is presently the most prevalent health problem affecting children living not only in the industrialized world, but in many low and middle-income countries as well. The so called “obesogenic environment” has penetrated much faster and as a consequence obesity has risen more rapidly in poor areas. However, in whatever country, a strong association between social inequality and obesity rates is common.1 The exception are children in least developed regions where the opposite is true; the relationship changes as socioeconomic conditions improve among the poorest segment and obesity rates become higher among the “better off groups” within the lower socio-economic strata. As the authors of this extensive review demonstrate, most obesity prevention studies are carried out within the educational system, mostly for practical reasons; just as we look for our lost keys in the only lit spot when there is darkness around us.2 This is quite understandable as
implementation and evaluation of community programmes involving children, parents, environments and social conditions are quite difficult to undertake in other settings. We clearly know that without modifying home and social environment, prevention will hardly ever be effective. For example, the contribution of parents in the process of change plays a key factor for success, but engaging them is most difficult, possibly because they do not acknowledge child obesity as a problem, they lack time to devote to this task, grandmothers or other adults who are in direct care of children perceive that cost of healthy foods are beyond what they can afford. Since schools are mostly ranked according to their student’s scholastic achievement in language and maths, the possibility to effectively increase physical activity in terms of intensity and duration is low. Unless obesity prevention initiatives are integrated into the school curricula, their sustainability is at best poor.
Downloaded from http://ije.oxfordjournals.org/ at New York University on May 15, 2015
to inform public health policy and practice. The authors’ suggest these findings are widely applicable: I am less certain of this. The review contains a small number of studies from low and middle-income countries. Even if some of the USA-based studies were in disadvantaged communities the context is very different, and contextual factors that operate around nutrition and nutritional choices cannot be under-estimated. In any case, the studies are disappointingly unclear as to which interventions work best and are most cost-effective. The review does present some transferable lessons. The first is that single interventions are less likely to be successful; thus to address the complexity of childhood obesity, interventions operating at multiple levels are required. A second is that in the majority of studies, the benefit of the intervention was not sustainable beyond the study period, indicating that interventions must be embedded in the home and school environments of children. Furthermore, addressing obesity in one age-group is insufficient and will require engagement across the child’s
677
678
and at the time of weaning. The greatest risk occurs in large for gestational age infants (LGA) born to overweight mothers. The odds ratio of developing childhood obesity can be as high as 15:1 for LGA compared with normal weight babies. Because this phenomenon crosses generations, mothers who themselves were LGA are at higher risk of being overweight or obese when they become pregnant. Therefore, public health efforts should be focused on the fetal/infant period. This is clearly an important time but should not be the only basket in which to place our eggs.4,5 Perhaps by now we should all learn from our mistakes and do “what needs to be done” despite the difficulties. We have enough data on doing “what is doable” but “does not work”.
References 1. Gupta N, Goel K, Shah P, Misra A Childhood obesity in developing countries: epidemiology, determinants, and prevention. Endocr Rev. 2012;33:48–70. 2. Swinburn B, Sacks G, Hall K, Mc Pherson K, Finegood D, Moodie M, Gortmaker S. The global epidemic pandemia shaped by global drivers and local environments. Lancet 2011;378:804–814. 3. Kain J, Uauy R, Concha F, Leyton B, Bustos N, Salazar G, Lobos L, Vio F. School-Based Obesity Prevention Interventions for Chilean Children During the Past Decades: Lessons Learned. Adv. Nutr 2012;3:616S–621S. 4. Uauy R, Kain J, Corvalan C. How can the developmental origins of health and disease (DOHaD) hypothesis contribute to improving health in developing countries? AJCN 2011;94(6 Suppl): 1759S–1764S. 5. Atkinson R, Pietrobelli A, Uauy R and Macdonald I. Are we attacking the wrong targets in the fight against obesity? The importance of intervention in women of childbearing age. IJO 2012;36: 1259–1260.
Downloaded from http://ije.oxfordjournals.org/ at New York University on May 15, 2015
Extra-curricular physical activity is a possibility but only if the school and parents are committed to support its implementation.3 Most of the published work on obesity interventions in children has been carried out in high-income countries. Only five of fifty-five studies analysed in the Cochrane Review were carried out in developing countries and of those only one in Asia (Thailand), even though the rise in obesity is being regarded as an emergent public health problem in China, Malaysia and the Gulf states. This systematic review (in contrast to older versions) includes nonrandomized controlled studies. This is a welcome addition, despite the risk of selection bias; often it is virtually impossible to randomly allocate schools to specific interventions. It is not unusual that interventions are implemented in locations where children have higher obesity prevalence since here is where the pressure to “do something about it” is greatest. This is not only methodologically undesirable, but it complicates the evaluation of potentially successful interventions. Most of the participants in this review were children 612 years of age. As has been shown, the rise in obesity starts much earlier, so prevention should begin earlier if we are seeking to succeed. This review considered the 0-5 age group, but as the authors point out “further breakdown by age was not possible given the small number of studies”. In this age group, only 8 studies met the inclusion criteria and of those, only one targeted infants under 3 years of age. Clearly, there is a lack of studies during infancy and early childhood, despite that the evidence that at earlier ages the chance of success is greatest. More over the analysis of predictive risk factors suggests that the time for effective action is really before conception, thus our efforts should focus on what occurs at preconception, during pregnancy
International Journal of Epidemiology, 2014, Vol. 43, No. 3
COCHRANE COLUMN Taryn Young, Charles S Wiysonge1
This column highlights Cochrane Reviews relevant to public health to stimulate debate about the review findings, their application, or methodological aspects that the reviews raise. In this issue, we look at a review summarizing interventions to prevent obesity in children. Anel Schoonees from South Africa summarised the Cochrane Review conducted by Walters and colleagues; and Maylene Shung King from South Africa, and Ricardo Uauy and Juliana Kain from Chile have written commentaries.
1
Centre for Evidence-based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa. E-mail: [email protected]. Website: www.sun.ac.za/cebhc
Anel Schoonees Centre for Evidence-based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, South Africa. E-mail: [email protected] summarized this Cochrane Review.
Background More and more children worldwide are overweight or obese, increasing their risk of medical problems including non-communicable diseases, and psychosocial problems including self-esteem, depression and bullying. A team from Australia, the United Kingdom and Hong Kong reviewed trials that evaluated interventions promoting healthier diets and increased physical activity to prevent children from becoming overweight and obese.
Methods The last search for the Cochrane Review was conducted in March 2010. Randomised and non-randomised controlled trials of at least 12 weeks duration that compared interventions targeting dietary behaviour, physical activity, or both with no intervention or a different intervention in children aged from 0 to 18 years old were included. Body mass index (BMI) was the main outcome.
Results Fifty-five studies were included, 50 in high-income countries, mostly North America. Thirty-nine studies included children aged between 6 and 12 years and 41 studies ranged between 12 and 52 weeks. The most common
setting for interventions was schools in 43 studies. The meta-analysis included 37 studies (27 946 children). A funnel plot suggested that some small studies that did not demonstrate an effect may not have been published, potentially influencing the meta-analysis. Table 1 shows the review’s main findings, including quantification of the effect size and consistency of findings. The review authors did not assess quality of the evidence with GRADE.
Conclusion Short-term obesity prevention interventions for children can be effective if carefully and thoroughly planned, implemented, monitored and regularly evaluated. Trials with long-term follow-up are needed. It remains unclear which specific dietary (such as a focus on increasing vegetable and fruit intake) or which physical activity (such as mandatory participation in school sport) components are the most effective. The full text of the review is available in The Cochrane Library: Waters E, de Silva-Sanigorski A, Hall BJ, Brown T, Campbell KJ, Gao Y, Armstrong R, Prosser L, Summerbell CD. Interventions for preventing obesity in children. Cochrane Database of Systematic Reviews 2011, Issue 12. Art. No.: CD001871. DOI: 10.1002/14651858. CD001871.pub3.
675
Downloaded from http://ije.oxfordjournals.org/ at New York University on May 15, 2015
Interventions for preventing obesity in children
676
International Journal of Epidemiology, 2014, Vol. 43, No. 3
Table 1. Effects of interventions on body mass index (kg/m2) Study characteristics
Subgroup
Number of trials
Number of children
Standardised mean difference
Heterogeneity (I2)
(95% confidence interval)* Type of intervention
Age
Study setting
Risk of bias
16 6 27
9245 2793 15 908
0.11 0.12 0.18
( 0.19 to 0.02) ( 0.28 to 0.05) ( 0.27 to 0.09)
66% 76% 82%
8 31 10 35 6 8 35 14 21 22 6
1815 18 983 7148 22 904 4086 956 17 003 10 943 5369 16 576 6001
0.26 0.15 0.09 0.14 0.09 0.28 0.17 0.12 0.16 0.14 0.16
( ( ( ( ( ( ( ( ( ( (
85% 79% 79% 79% 56% 87% 80% 79% 68% 85% 74%
0.53 to 0.00) 0.23 to 0.08) 0.20 to 0.03) 0.21 to 0.08) 0.20 to 0.02) 0.72 to 0.16) 0.25 to 0.09) 0.21 to 0.03) 0.27 to 0.05) 0.23 to 0.05) 0.27 to 0.04)
*Effect sizes shown are for combined physical activity and dietary interventions, unless otherwise stated.
Commentary: Childhood obesity: A growing dilemma for public health interventions and research alike Maylene Shung King Health Economics Unit, School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa. Email: [email protected]
Childhood obesity is a growing public health problem that cuts across country, socio-economic, and cultural contexts. It has implications for the immediate health of children, as well as being a pre-cursor for non-communicable diseases in adulthood. A recent South African review article showed that the prevalence of overweight and obesity in primary school children has increased more than ten-fold in ten years.1 This is mirrored on the wider African continent where, despite persistent hunger and under-nutrition, overweight and obesity in children is estimated to have doubled in recent years.2,3 Roussouw et al describe the unhappy coexistence of a dual burden of disease: “…undernutrition and overweight or obesity are found in the same populations, in the same households, and even in the same children.” This reflects the complexity that overweight and obesity presents, and implies that interventions to address these phenomena must consider this complexity.
The Cochrane Review outlines the state of play of intervention programmes to reduce and avert childhood obesity. It showcases the growing attention given to childhood obesity in high-income countries, while highlighting the paucity of published intervention research from low and middle-income countries – an indicator suggesting that childhood obesity as a public health problem is still eclipsed by other priority health problems. The review appropriately groups studies according to interventions by age groups and thus highlights the unsurprising emphasises on primary school children. A World Bank review of school health services globally corroborates that nutrition is a key focus in school health programmes.2 The review highlights challenges and opportunities. The great variety of interventions, and the variable contexts in which they are applied, presents a challenge for the metaanalysis, as well as for the conclusions that may be drawn
Downloaded from http://ije.oxfordjournals.org/ at New York University on May 15, 2015
Duration of interventions
Physical activity interventions Dietary interventions Combined physical activity and dietary interventions Age 0 to 5 years Age 6 to 12 years Age 13 to 18 years Education setting only Education and other settings Non-education setting Duration 12 months Duration > 12 months Low risk of bias Unclear risk of bias High risk of bias
International Journal of Epidemiology, 2014, Vol. 43, No. 3
lifespan. Lastly, the answer to childhood obesity, as with many health problems, may not reside with specific narrow interventions, but is probably best addressed ‘up-stream’, where key determinants of health are located. In this instance part of the answer may lie in targeting the food and beverage industry to reduce the production of the numerous unhealthy products that put children and their families at risk of poor health and disease.3
References 1. Rossouw HA, Grant CC, Viljoen M. Overweight and obesity in children and adolescents: The South African problem. S Afr J Sci. 2012;108. 2. De Onis M, Blo¨ssner M, Borghi E. Global prevalence and trends of overweight and obesity among preschool children. Am J Clin Nutr. 2010;92:1257–1264. 3. De Onis M, Blo¨ssner M. Prevalence and trends of overweight among preschool children in developing countries. Am J Clin Nutr. 2000;72:1032–1039.
Commentary: Interventions for preventing obesity in children (Review) Ricardo Uauy and Juliana Kain Institute of Food Technology and Nutrition (INTA), University of Chile, Chile. E-mail: [email protected]
Obesity is presently the most prevalent health problem affecting children living not only in the industrialized world, but in many low and middle-income countries as well. The so called “obesogenic environment” has penetrated much faster and as a consequence obesity has risen more rapidly in poor areas. However, in whatever country, a strong association between social inequality and obesity rates is common.1 The exception are children in least developed regions where the opposite is true; the relationship changes as socioeconomic conditions improve among the poorest segment and obesity rates become higher among the “better off groups” within the lower socio-economic strata. As the authors of this extensive review demonstrate, most obesity prevention studies are carried out within the educational system, mostly for practical reasons; just as we look for our lost keys in the only lit spot when there is darkness around us.2 This is quite understandable as
implementation and evaluation of community programmes involving children, parents, environments and social conditions are quite difficult to undertake in other settings. We clearly know that without modifying home and social environment, prevention will hardly ever be effective. For example, the contribution of parents in the process of change plays a key factor for success, but engaging them is most difficult, possibly because they do not acknowledge child obesity as a problem, they lack time to devote to this task, grandmothers or other adults who are in direct care of children perceive that cost of healthy foods are beyond what they can afford. Since schools are mostly ranked according to their student’s scholastic achievement in language and maths, the possibility to effectively increase physical activity in terms of intensity and duration is low. Unless obesity prevention initiatives are integrated into the school curricula, their sustainability is at best poor.
Downloaded from http://ije.oxfordjournals.org/ at New York University on May 15, 2015
to inform public health policy and practice. The authors’ suggest these findings are widely applicable: I am less certain of this. The review contains a small number of studies from low and middle-income countries. Even if some of the USA-based studies were in disadvantaged communities the context is very different, and contextual factors that operate around nutrition and nutritional choices cannot be under-estimated. In any case, the studies are disappointingly unclear as to which interventions work best and are most cost-effective. The review does present some transferable lessons. The first is that single interventions are less likely to be successful; thus to address the complexity of childhood obesity, interventions operating at multiple levels are required. A second is that in the majority of studies, the benefit of the intervention was not sustainable beyond the study period, indicating that interventions must be embedded in the home and school environments of children. Furthermore, addressing obesity in one age-group is insufficient and will require engagement across the child’s
677
678
and at the time of weaning. The greatest risk occurs in large for gestational age infants (LGA) born to overweight mothers. The odds ratio of developing childhood obesity can be as high as 15:1 for LGA compared with normal weight babies. Because this phenomenon crosses generations, mothers who themselves were LGA are at higher risk of being overweight or obese when they become pregnant. Therefore, public health efforts should be focused on the fetal/infant period. This is clearly an important time but should not be the only basket in which to place our eggs.4,5 Perhaps by now we should all learn from our mistakes and do “what needs to be done” despite the difficulties. We have enough data on doing “what is doable” but “does not work”.
References 1. Gupta N, Goel K, Shah P, Misra A Childhood obesity in developing countries: epidemiology, determinants, and prevention. Endocr Rev. 2012;33:48–70. 2. Swinburn B, Sacks G, Hall K, Mc Pherson K, Finegood D, Moodie M, Gortmaker S. The global epidemic pandemia shaped by global drivers and local environments. Lancet 2011;378:804–814. 3. Kain J, Uauy R, Concha F, Leyton B, Bustos N, Salazar G, Lobos L, Vio F. School-Based Obesity Prevention Interventions for Chilean Children During the Past Decades: Lessons Learned. Adv. Nutr 2012;3:616S–621S. 4. Uauy R, Kain J, Corvalan C. How can the developmental origins of health and disease (DOHaD) hypothesis contribute to improving health in developing countries? AJCN 2011;94(6 Suppl): 1759S–1764S. 5. Atkinson R, Pietrobelli A, Uauy R and Macdonald I. Are we attacking the wrong targets in the fight against obesity? The importance of intervention in women of childbearing age. IJO 2012;36: 1259–1260.
Downloaded from http://ije.oxfordjournals.org/ at New York University on May 15, 2015
Extra-curricular physical activity is a possibility but only if the school and parents are committed to support its implementation.3 Most of the published work on obesity interventions in children has been carried out in high-income countries. Only five of fifty-five studies analysed in the Cochrane Review were carried out in developing countries and of those only one in Asia (Thailand), even though the rise in obesity is being regarded as an emergent public health problem in China, Malaysia and the Gulf states. This systematic review (in contrast to older versions) includes nonrandomized controlled studies. This is a welcome addition, despite the risk of selection bias; often it is virtually impossible to randomly allocate schools to specific interventions. It is not unusual that interventions are implemented in locations where children have higher obesity prevalence since here is where the pressure to “do something about it” is greatest. This is not only methodologically undesirable, but it complicates the evaluation of potentially successful interventions. Most of the participants in this review were children 612 years of age. As has been shown, the rise in obesity starts much earlier, so prevention should begin earlier if we are seeking to succeed. This review considered the 0-5 age group, but as the authors point out “further breakdown by age was not possible given the small number of studies”. In this age group, only 8 studies met the inclusion criteria and of those, only one targeted infants under 3 years of age. Clearly, there is a lack of studies during infancy and early childhood, despite that the evidence that at earlier ages the chance of success is greatest. More over the analysis of predictive risk factors suggests that the time for effective action is really before conception, thus our efforts should focus on what occurs at preconception, during pregnancy
International Journal of Epidemiology, 2014, Vol. 43, No. 3
