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Do dietary and activity strategies help prevent obesity in children?

The highly cited Cochrane review ‘Interventions for preventing obesity in children’ has undergone a major update by researchers at Fuse from Durham University.

The reviews show that a range of physical activity interventions, with or without a diet element, can have a modest beneficial effect on obesity in children and adolescents, without affecting health inequalities and without serious adverse events.

One of Cochrane’s most cited reviews and encompassing 153 studies at its last update in 2019, it has now been broken down into smaller age ranges. Cochrane has published the two reviews focusing on studies of interventions aimed at children aged 5-11 and 12-18.

“Those responsible for public health policy and implementing these types of interventions need this information.”

Professor Carolyn Summerbell, Deputy Director of Fuse

The ‘parent’ Cochrane review of interventions to prevent obesity in children focused on children aged 0-18, and has been updated five times since it was first published with seven studies in 2000.

Cochrane and the author team decided to divide it into four reviews for several reasons. Alongside the increased volume of studies, the need to consider children’s different developmental stages and the development of research methods and searching led to the change.

The review has been broken down by age. Today sees the publication of the primary school (5-11) and secondary school children and adolescents (12-18) reviews. The pre-school (2-4) review is due to be published later this year.

5-11 years Childhood Obesity Updates_Cochrane Review 2024 (2)

updated 12-18 years Childhood Obesity Updates_Cochrane Review 2024

These reviews are the first to be published from these new groupings. The research team included 74 studies in the 12-18 age group review and 172 studies in the 5-11 one. Of these, 54 and 149 studies, respectively, contributed to the meta-analyses.

They looked at body mass index (BMI), age- and sex-standardised BMI (zBMI) and percentile BMI, reported in randomised controlled trials with interventions aimed at changing diet, physical activity levels (including sedentary time) or both. The trials were delivered in any setting, with most being in schools.

In the younger age-group, they found that a range of school-based physical activity interventions, alone or in combination with diet interventions, may have a modest beneficial effect on obesity in childhood at short- and medium-term follow-up (between 3 and 15 months), but not at long term follow-up (15 months or more). Diet interventions alone may result in little to no difference.

In the older age group, they found at medium- and long-term follow-up (9 months or more) physical activity interventions may have a small beneficial effect on reducing BMI gain, whereas diet alone or diet plus physical activity interventions may result in little to no difference. They found no effect of interventions on zBMI. Certainty in evidence was low to very low.

They found no adverse effects of the interventions in either age group review and, although the information was limited, there is no evidence of increased inequalities.

Professor Carolyn Summerbell, Durham University and Deputy Director of Fuse, the Centre for Translational Research in Public Health, is the lead senior author of the updated reviews. She said:

“The number of new trials included in these reviews allows us to be more confident about the overall small but positive impact of this type of public health intervention to prevent obesity in school age children and adolescents. Indeed, I doubt more of the same school-based trials which target individual behaviour change would change these findings.

“But did these interventions increase health inequalities? Although many studies didn’t report on this, those that did suggest there was no impact. Those responsible for public health policy and implementing these types of interventions need this information.

“What we do know is that some children and adolescents who are most at risk of obesity don’t engage well with school, or school-based interventions, or are often excluded from trials. Knowing how these interventions work in community settings such as local youth clubs and faith-based groups, and in children and adolescents with disabilities, remains a gap in the evidence base.”

The same team has been investigating, using more complex analytic syntheses, what specific characteristics of these interventions make them more effective in reducing BMI and make them more equitable. The findings will be published in research papers later this year.

The reviews are informing guidance on childhood obesity, with the National Institute for Health and Care Excellence (NICE) including the analyses in their new guidance due to be published in Autum 2024.

Read the reviews:

Last modified: Mon, 20 May 2024 11:15:46 BST