Prevention of childhood obesity is an international public health priority given the significant impact of obesity on acute and chronic diseases, general health, development and well-being. The international evidence base for strategies to prevent obesity is very large and is accumulating rapidly. This is an update of a previous review.
To determine the effectiveness of interventions intended to prevent obesity in children, assessed by change in body-mass index (BMI) and BMI z-score (zBMI).
We searched CENTRAL, MEDLINE, Embase, PsychINFO and CINAHL in June 2015. We re-ran the search from June 2015 to January 2018 and included a search of trial registers.
Randomised controlled trials (RCTs) of diet (D) or physical activity (PA) interventions, or combined D+PA interventions, for preventing overweight or obesity in children (0-17 years) that reported outcomes at a minimum of 12 weeks from baseline.
Data collection and analysis
Two authors independently extracted data, assessed risk-of-bias and evaluated overall certainty of the evidence using GRADE. We extracted data on adiposity outcomes, sociodemographic characteristics, adverse event, intervention process and costs. We meta-analysed data as guided by the Cochrane Handbook for Systematic Reviews of Interventions and presented separate meta-analyses by age group for child 0 to 5 years, 6 to12 years, and 13 to18 years afor zBMI and BMI,
We included 153 RCTs, mostly from the USA or Europe. Thirteen studies were based in upper-middle-income countries (UMIC: Brazil, Ecuador, Lebanon, Mexico, Thailand, Turkey, US-Mexico border), and one was based in a lower middle-income country (LMIC: Egypt). The majority (85) targeted children aged 6 to 12 years.
Children aged 0-5 years:
There is moderate-certainty evidence from 16 RCTs (n = 6261) that D+PA interventions, compared with control, reduced BMI (mean difference (MD) −0.07 kg/m2, 95% confidence interval (CI) −0.14 to −0.01), and had a similar effect (11 RCTs, n = 5536) on zBMI (MD −0.11, 95% CI −0.21 to 0.01). Neither diet (moderate-certainty evidence) nor physical activity interventions alone (high-certainty evidence) compared with control reduced BMI (physical activity alone: MD −0.22 kg/m2, 95% CI −0.44 to 0.01) or zBMI (diet alone: MD −0.14, 95% CI −0.32 to 0.04; physical activity alone: MD 0.01, 95% CI −0.10 to 0.13) in children aged 0-5 years.
Children aged 6 to 12 years:
There is moderate-certainty evidence from 14 RCTs (n = 16,410) that physical activity interventions, compared with control, reduced BMI (MD −0.10 kg/m2, 95% CI −0.14 to −0.05). However, there is moderate-certainty evidence that they had little or no effect on zBMI (MD −0.02, 95% CI −0.06 to 0.02). There is low-certainty evidence from 20 RCTs (n = 24,043) that D+PA compared with control, reduced zBMI (MD −0.05 kg/m2, 95% CI −0.10 to −0.01). There is high-certainty evidence that diet interventions, compared with control, had little impact on zBMI (MD −0.03, 95% CI −0.06 to 0.01) or BMI (−0.02 kg/m2, 95% CI −0.11 to 0.06).
Children aged 13 to 18 years:
There is very-low certainty evidence that physical activity interventions, compared with control reduced BMI (MD −1.53 kg/m2, 95% CI −2.67 to −0.39; 4 RCTs; n = 720); and low certainty evidence for a reduction in zBMI (MD -0.2, 95% CI −0.3 to -0.1; 1 RCT; n = 100). There is low-certainty evidence from eight RCTs (n = 16,583) that D+PA compared with control, had no effect on BMI (MD −0.02 kg/m2, 95% CI −0.10 to 0.05); or zBMI (MD 0.01, 95% CI −0.05 to 0.07; 6 RCTs; n = 16,543). Evidence from two RCTs (low-certainty evidence; n = 294) found no effect of diet interventions on BMI.
Direct comparisons of interventions:
Two RCTs reported data directly comparing diet with either physical activity or D+PA interventions for children aged 6 – 12 years and reported no differences.
Heterogeneity was apparent in the results from all three age groups, which could not be entirely explained by setting or duration of the interventions. Where reported, interventions did not appear to result in adverse effects (16 RCTs) or increase health inequalities (gender: 30 RCTs; socioeconomic status: 18 RCTs), although relatively few studies examined these factors.
Re-running the searches in January 2018 identified 315 records with potential relevance to this review, which will be synthesised in the next update.
Interventions that include D+PA can reduce the risk of obesity (zBMI and BMI) in young children aged 0 to 5 years. There is weaker evidence from a single study that dietary interventions may be beneficial. However, interventions that focus only on physical activity do not appear to be effective in children of this age.
In contrast, interventions that only focus on physical activity can reduce the risk of obesity (BMI) in children aged 6 to 12 years, and adolescents aged 13 to 18 years. In these age groups, there is no evidence that interventions that only focus on diet are effective, and some evidence that D+PA may be effective but we are very uncertain about this result. This review highlights a lack of evidence on, and the necessity for, RCTs to measure and report adverse effects and health inequalities.
The interventions included in this update mainly focused on changing individual (personal) behaviours and were conducted in childcare centres, schools, homes and healthcare centres. About 15% of the interventions were conducted in the wider community, mainly local public community or recreation centres. If we are serious about tackling childhood obesity, this will require the implementation of these wider community-level interventions, together with upstream environmental and policy interventions
Evidence from newly identified RCTs from UMIC and LMIC countries is an important contribution for this updated review, in terms of context and external validity, particularly for policy-makers in those countries. This updated review also confirms, importantly, that interventions to prevent childhood obesity do not appear to result in adverse effects or health inequalities. The review will not be updated in its current form. To manage the growth in RCTs of child obesity prevention interventions, in future, this review will be split into three separate reviews based on child age.
- Systematic Review
- Obesity prevention
- Children 0-18 years