Interventions for preventing obesity in children: a Cochrane review update Clinical

Interventions for preventing obesity in children: a Cochrane review update

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Clinical

Public health questions

• Do interventions intended to prevent obesity in children work?– Do they reduce BMI or the prevalence of obesity/overweight?– Do they lead to positive changes in dietary- or physical activity-related

behaviours?• Can we answer: “What works for whom, why and for what

cost?”

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Source: 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

Context• Childhood obesity can cause social, psychological and health problems,

and is linked to obesity later in life and poor health outcomes as an adult. • In children, adolescents and adults in a wide range of countries (including

more recently, middle- and low-income countries) high and increasing rates of overweight and obesity have been reported over the last few decades.

• Governments around the world are being urged to take action to prevent childhood obesity and to address its underlying determinants.

• The impact of interventions on preventing obesity, the extent that they work equitably, their safety and how they work, remains poorly understood.

• The previous version of this updated review was based on literature searches in 2005.


Methods• The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE,

EMBASE, PsycINFO and CINAHL were searched, along with grey literature.• Meta-analysis was used to investigate the impact of interventions on BMI,

with means and standard deviations (SDs) used to calculate standardised mean differences (SMDs) between groups.

• Effectiveness was summarised according to a range of outcomes (measures of adiposity, behaviour, impact on equity and adverse/unintended effects), as well as maintenance/sustainability of effects.

• Implementation information was summarised according to the theoretical basis of the studies, whether process evaluations were conducted, the reporting of resources and other factors needed for implementation, and whether specific strategies were included to address disadvantage or diversity.


PICO(S) to assess eligible studies• Participants / Population: Children under 18 when recruited. Studies with

children who were already obese were eligible, if obesity was not a requirement for children to be included in the study.

• Intervention: Interventions/policies/programs for the prevention of childhood obesity that were in place for at least 12 weeks. Interventions designed for the treatment of childhood obesity were excluded.

• Comparison: Usual care or another active comparison.• Primary outcomes: Weight and height, per cent fat content, BMI,

ponderal index, skin-fold thickness, prevalence of overweight and obesity.• Studies: Studies that used a controlled study design (with or without

randomisation). If studies were randomised at a cluster level, a minimum of 6 clusters was required.


Description of eligible studies• A total of 55 studies are included in this update, an additional

36 studies compared to the previous version.• Most studies targeted children aged 6-12 years (n=39). • 41 studies tested interventions implemented for 12 months

or less, seven for 1 to 2 years, and seven for longer.• 50 studies were set in high-income countries, 4 were in

upper-middle-income countries (Brazil, Chile, Mexico), and one was in a lower middle-income country (Thailand).


Results• The meta-analysis included 37 studies (27,946 children) and

demonstrated that programmes were effective at reducing adiposity, but not all interventions were effective, and there was a high level of observed heterogeneity (I2=82%).

• Heterogeneity was apparent in all three age groups (0-5, 6-12, 13-18 years) and could not explained by design features of the studies.

• Only 8 studies reported on adverse effects and no evidence of adverse outcomes such as unhealthy dieting practices, increased prevalence of underweight or body image sensitivities was found.

• Health inequalities was examined in few studies, but interventions did not appear to increase these.


Standardised mean difference (BMI / zBMI)

Random effectsmeta-analysis

Favours experimental (intervention)

Meta-analysis37 (of 55) studies27,946 children

Overall-0.15kg/m2 (95% CI: -0.21 to -0.09)

13-18 years-0.09kg/m2 (95% CI -0.20 to 0.03)

6-12 years-0.15kg/m2 (95% CI -0.23 to -0.08)

0-5 years-0.26kg/m2 (95% CI:-0.53 to 0.00)

Favours control(no intervention)

Are the interventions ‘effective’?• Effect sizes may be ‘small’ for individuals, but significant on a

population scale.• A differential effect of -0.15 BMI was found among nearly

15,500 children in the intervention groups, which could be enough to shift a child from the overweight/obese category.

• The effect has clinical significance given the reach of these interventions.

• Implemented programs and policies must be sustained and continually evaluated.

Implications (so what?)

Conclusions: current findings• Evidence supports beneficial effects of child obesity prevention

programmes on BMI, particularly those targeted to children aged 6-12, but unexplained heterogeneity means that these findings must be interpreted with caution.

• A broad range of programme components were used in these studies and it’s not possible to distinguish which components contributed most to the beneficial effects.


Conclusions: current findingsThe following policies and strategies are likely to be promising:• school curriculum that includes healthy eating, physical activity and body

image• increased sessions for physical activity throughout the school week• improvements in nutritional quality of the food supply in schools• environments and cultural practices that support children eating healthier

foods and being active throughout each day• support for teachers and other staff to implement health promotion

strategies and activities (e.g. professional development, capacity building activities)

• parent support and home activities that encourage children to be more active, eat more nutritious foods and spend less time in screen based activities


Conclusions: future research• Study and evaluation designs need to be strengthened, and

reporting extended to capture process and implementation factors, outcomes in relation to measures of equity, longer term outcomes, potential harms and costs.

• Research must move towards identifying how effective intervention components can be embedded within health, education and care systems and achieve long term sustainable impacts.


Useful links• Cochrane Journal Club discussion points

• Interventions for preventing obesity in children


Documents

Interventions for preventing obesity in children: a Cochrane review update Clinical