***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background There is some evidence that school-based interventions are effective in preventing childhood obesity . However , longer term outcomes , equity of effects and cost-effectiveness of interventions have not been assessed . The aim of this trial is to assess the clinical and cost-effectiveness of a multi-component intervention programme targeting the school and family environment through primary schools , in preventing obesity in 6–7 year old children , compared to usual practice . Methods This cluster r and omised controlled trial is set in 54 primary schools within the West Midl and s , UK , including a multi-ethnic , socioeconomically diverse population of children aged 6–7 years . The 12-month intervention consists of healthy diet and physical activity promotion . These include : activities to increase time spent doing physical activity within the school day , participation in the ‘ Villa Vitality ’ programme ( a programme that is delivered by an iconic sporting institution ( Aston Villa Football Club ) , which provides interactive learning opportunities for physical activity and healthy eating ) , healthy cooking skills workshops in school time for parents and children , and provision of information to families signposting local leisure opportunities . The primary ( clinical ) outcome is the difference in body mass index ( BMI ) z-scores between arms at 3 and 18 months post-intervention completion . Cost per Quality Adjusted Life Year ( QALY ) will also be assessed . The sample size estimate ( 1000 children split across 50 schools at follow-up ) is based on 90 % power to detect differences in BMI z-score of 0.25 ( estimated ICC ≤ 0.04 ) , assuming a correlation between baseline and follow-up BMI z-score of 0.9 . Treatment effects will be examined using mixed model ANCOVA . Primary analysis will adjust for baseline BMI z-score , and secondary analysis will adjust for pre-specified baseline school and child level covariates . Discussion The West Midl and s ActiVe lifestyle and healthy Eating in School children ( WAVES ) study is the first trial that will examine the cost-effectiveness and long term outcomes of a childhood obesity prevention programme in a multi-ethnic population , with a sufficient sample size to detect clinical ly important differences in adiposity . The intervention was developed using the Medical Research Council framework for complex interventions , and outcomes are measured objective ly , together with a comprehensive process evaluation . Trial registration Current Controlled Trials IS RCT N97000586 ( registered May 2010 ) Objective To investigate the effectiveness of a school based intervention to increase physical activity , reduce sedentary behaviour , and increase fruit and vegetable consumption in children . Design Cluster r and omised controlled trial . Setting 60 primary schools in the south west of Engl and . Participants Primary school children who were in school year 4 ( age 8 - 9 years ) at recruitment and baseline assessment , in year 5 during the intervention , and at the end of year 5 ( age 9 - 10 ) at follow-up assessment . Intervention The Active for Life Year 5 ( AFLY5 ) intervention consisted of teacher training , provision of lesson and child-parent interactive homework plans , all material s required for lessons and homework , and written material s for school newsletters and parents . The intervention was delivered when children were in school year 5 ( age 9 - 10 years ) . Schools allocated to control received st and ard teaching . Main outcome measures The pre-specified primary outcomes were accelerometer assessed minutes of moderate to vigorous physical activity per day , accelerometer assessed minutes of sedentary behaviour per day , and reported daily consumption of servings of fruit and vegetables . Results 60 schools with more than 2221 children were recruited ; valid data were available for fruit and vegetable consumption for 2121 children , for accelerometer assessed physical activity and sedentary behaviour for 1252 children , and for secondary outcomes for between 1825 and 2212 children for the main analyses . None of the three primary outcomes differed between children in schools allocated to the AFLY5 intervention and those allocated to the control group . The difference in means comparing the intervention group with the control group was –1.35 ( 95 % confidence interval –5.29 to 2.59 ) minutes per day for moderate to vigorous physical activity , –0.11 ( –9.71 to 9.49 ) minutes per day for sedentary behaviour , and 0.08 ( –0.12 to 0.28 ) servings per day for fruit and vegetable consumption . The intervention was effective for three out of nine of the secondary outcomes after multiple testing was taken into account : self reported time spent in screen viewing at the weekend ( –21 ( –37 to –4 ) minutes per day ) , self reported servings of snacks per day ( –0.22 ( –0.38 to –0.05 ) ) , and servings of high energy drinks per day ( –0.26 ( –0.43 to –0.10 ) ) were all reduced . Results from a series of sensitivity analyses testing different assumptions about missing data and from per protocol analyses produced similar results . Conclusion The findings suggest that the AFLY5 school based intervention is not effective at increasing levels of physical activity , decreasing sedentary behaviour , and increasing fruit and vegetable consumption in primary school children . Change in these activities may require more intensive behavioural interventions with children or upstream interventions at the family and societal level , as well as at the school environment level . These findings have relevance for research ers , policy makers , public health practitioners , and doctors who are involved in health promotion , policy making , and commissioning services . Trial registration Current Controlled Trials IS RCT N50133740 Background Schools are key setting s for childhood obesity prevention , and the location for many intervention studies . This qualitative study aims to explore parent and child experiences of the  WAVES study obesity prevention intervention  , in order to gain underst and ing of the mechanisms by which the intervention results in behaviour change , and provide context to support interpretation of the main trial results . Methods Focus groups were held with 30 parents and 62 children ( aged 6 - 7 years ) from primary schools in the West Midl and s , UK . Data analysis ( conducted using NVivo 10 ) was guided by the Framework Approach . Results Three over-arching themes were identified : ‘ Impact ’ , ‘ Sustainability ’ and ‘ Responsibilities ’ , under which sub-themes were determined . Participants were supportive of the school-based intervention . Parental involvement and the influential role of the teacher were seen as key ingredients for success in promoting consistent messages and empowering some parents to make positive behavioural changes at home . Parents recognised that whilst they held the primary responsibility for obesity prevention in their children , they faced a number of barriers to healthier lifestyles , and agreed that schools have an important role to play . Conclusions This study enabled us to better underst and aspects of the WAVES study intervention programme that have the potential to initiate positive behaviour changes in families , and indicated that a combination of pathways influenced such changes . Pathways included : increasing capability through improving knowledge and skills of children and parents ; increasing motivation through parental empowerment and role modelling ; and the direct provision of opportunities to lead healthier lifestyles . Strategies to sustain behaviour changes , and the school role in supporting these , are important considerations OBJECTIVE To examine whether dietary intake reported by school-aged children relates to the chronological period of data collection . DESIGN Cross-sectional surveys in 39 countries in different monthly periods of the 2009 - 2010 school year . SETTING S Question naires were completed in schools anonymously . PARTICIPANTS Children from 39 countries , aged 11 , 13 , and 15 years ( n = 209,320 ) . MAIN OUTCOME MEASURES Daily consumption of fruits , vegetables , sweets , and soft drinks  , derived from a food frequency question naire . ANALYSIS Multivariate logistic regression ( applied for 3 countries ) ; 2-level r and om intercept logistic regression ( applied for 36 countries ) . RESULTS Monthly variations in food intake among students from Canada , Engl and , and Norway , where data collection took place almost all months of the school year , revealed significantly lower daily consumption of food items in January to February . A 2-level r and om intercept logistic regression model for 36 countries , where question naires were administered in relatively shorter periods , indicated the lowest likelihood of fruit and soft drink consumption when the data were collected in March to April ( β = -0.30 ; P = .006 , compared with October to December ) and in January to February ( β = -0.65 ; P = .018 , compared with May to June ) , respectively . CONCLUSIONS AND IMPLICATION S The chronological period of data collection must be considered when comparing children 's reported food consumption , but this effect is small relative to cross-national variations in dietary patterns BACKGROUND / OBJECTIVES Childhood obesity is a major public health concern but evidence -based approaches to tackle this epidemic sustainably are still lacking . The Identification and prevention of Dietary- and lifestyle-induced health EFfects In Children and infantS ( IDEFICS ) study investigated the aetiology of childhood obesity and developed a primary prevention programme . Here , we report on the effects of the IDEFICS intervention on indicators of body fatness . SUBJECTS/ METHODS The intervention modules addressed the community , school and parental level , focusing on diet , physical activity and stress-related lifestyle factors .  A cohort of 16,228 children aged 2 - 9.9 years - about 2000 per country - was equally divided over intervention and control regions . ( Participating countries were Sweden , Germany , Estonia , Hungary , Cyprus , Italy , Spain and Belgium . ) We compared the prevalence of overweight/obesity and mean values of body mass index z-score , per cent body fat and waist-to-height ratio over 2 years of follow-up . Mixed models adjusting for age and socioeconomic status of the parents and with an additional r and om effect for country accounted for the clustered study design . RESULTS The prevalence of overweight and obesity increased in both the intervention and control group from 18.0 % at baseline to 22.9 % at follow-up in the control group and from 19.0 % to 23.6 % in the intervention group . The difference in changes between control and intervention was not statistically significant . For the cohort as a whole , the changes in indicators of body fatness did not show any clinical ly relevant differences between the intervention and control groups . Changes in favour of intervention treatment in some indicators were counterbalanced by changes in favour of the control group in some other indicators . CONCLUSIONS Over the 2-year-observation period , the IDEFICS primary prevention programme for childhood obesity has not been successful in reducing the prevalence of overweight and obesity nor in improving indicators of body fatness in the target population as a whole Background The implementation of a complex intervention is heavily influenced by individual context . Variation in implementation and tailoring of the intervention to the particular context will occur , even in a trial setting . It is recognised that in trials , evaluating the process of implementation of a complex intervention is important , yet process evaluation methods are rarely reported . The WAVES study is a cluster r and omised controlled trial to evaluate the effectiveness of an obesity prevention intervention programme targeting children aged 6 - 7 years , delivered by teachers in primary schools across the West Midl and s , UK . The intervention promoted activities encouraging physical activity and healthy eating . This paper presents the methods used to assess implementation of the intervention . Methods Previous literature was used to identify the dimensions of intervention process and implementation to be assessed , including adherence , exposure , quality of delivery , participant responsiveness , context , and programme differentiation . Results Multiple methods and tools were developed to capture information on all these dimensions . These included observations , logbooks , qualitative evaluation , question naires and research team reflection . Discussion Data collection posed several challenges , predominantly when relying on teachers to complete paperwork , which they saw as burdensome on top of their teaching responsibilities . However , the use of multiple methods helped to ensure data on each dimension , where possible , was collected using more than one method . This also allowed for triangulation of the findings when several data sources on any one dimension were available . Conclusions We have reported a comprehensive approach to the assessment of the implementation and processes of a complex childhood obesity prevention intervention within a cluster r and omised controlled trial . These approaches can be transferred and adapted for use in other complex intervention trials . Trial registration numberIS RCT Objective To assess feasibility and acceptability of a multifaceted , culturally appropriate intervention for preventing obesity in South Asian children , and to obtain data to inform sample size for a definitive trial . Design Phase II feasibility study of a complex intervention . Setting 8 primary schools in inner city Birmingham , UK , within population s that are predominantly South Asian . Participants 1090 children aged 6–8 years took part in the intervention . 571 ( 85.9 % from South Asian background ) underwent baseline measures . 85.5 % ( n=488 ) were followed up 2 years later . Interventions The 1-year intervention consisted of school-based and family-based activities , targeting dietary and physical activity behaviours . The intervention was modified and refined throughout the period of delivery . Main outcome measures Acceptability and feasibility of the intervention and of measurements required to assess outcomes in a definitive trial . The difference in body mass index ( BMI ) z-score between arms was used to inform sample size calculations for a definitive trial . Results Some intervention components ( increasing school physical activity opportunities , family cooking skills workshops , signposting of local leisure facilities and attending day event at a football club )  were feasible and acceptable . Other components were acceptable , but not feasible . Promoting walking groups was neither acceptable nor feasible . At follow-up , children in the intervention compared with the control group were less likely to be obese ( OR 0.41 ; 0.19 to 0.89 ) , and had lower adjusted BMI z-score ( −0.15 kg/m2 ; 95 % CI −0.27 to −0.03 ) . Conclusions The feasibility study informed components for an intervention programme . The 
    Output:
    
The primary analyses suggest that this experiential focused intervention had no statistically significant effect on BMI z score or on preventing childhood obesity .
Schools are unlikely to impact on the childhood obesity epidemic by incorporating such interventions without wider support across multiple sectors and environments .
Correspondence to : P Adab p.adab@bham.ac.uk Cite this as : BMJ 2018;360:k211 http://dx.doi.org/10.1136/bmj.k211 Accepted : 19 December 2017 WhAT IS AlReAdy knoWn on ThIS TopIC Comprehensive systematic review s have suggested that school based interventions could be effective in preventing childhood obesity in high income countries Heterogeneity in intervention components and outcomes limit practical recommendations Furthermore , inconsistent findings in relation to differential effects on subgroups , and impact on inequalities , limited data on potential harms , process measures , and long term effects , as well as lack of data on cost effectiveness , restrict interpretation and wider applicability WhAT ThIS STudy AddS The WAVES study evaluated a theoretically informed , skills based intervention targeting children ’s diet and physical activity behaviours through schools and families It did not result in any meaningful effect on adiposity , dietary intake , or physical activity after 15 or 30 months Although such interventions can fulfil the responsibility of schools for wider education , without upstream support they are unlikely to halt the childhood obesity