Obesity, diet and nutrition: a review of reviews

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Introduction

This review aimed to address two questions:

1. What universal (population level), whole system or settings based programmes and interventions are effective in preventing overweight and obesity in children?
2. What universal, whole system or settings based interventions are effective in preventing overweight and obesity in adults aged 18 to 65 years?

Main points

How up to date is this evidence?

Searches were run between October and November 2017. For children, evidence published from 2014 onwards was included. For adults, evidence from 2008 onwards was included to reflect differences from the original 2014 review.

What we found

• Twenty-four systematic reviews were identified across the two questions, with the following key findings being identified:

Social media and game-based nutrition interventions:

• Some evidence of positive effects on knowledge, attitudes, fruit and vegetable intake, and weight or BMI, but findings were not conclusive.
• Some evidence that electronic games improve knowledge, attitudes, and weight or BMI, but evidence was not conclusive.

Socio-ecological approaches to childhood obesity prevention:

• Some evidence that interventions targeting three or four levels of the socio-ecological model, including school or community environments, improve weight outcomes, but evidence was not conclusive.

Universal parent support interventions:

• Moderate evidence that face-to-face counselling of parents improves children’s diets.
• Some evidence that telephone counselling or group-based education is effective for changing diets, but not conclusive.
• Evidence for effects on weight outcomes was inconsistent.

School policy and environment interventions:

• Some evidence that changing school food environments improves purchasing or consumption behaviours, but not conclusive.
• Some evidence that school policies targeting diet improve dietary behaviours, but not conclusive.
• Evidence for effects on weight outcomes was inconsistent.

Preschool interventions:

• Moderate quality evidence that multicomponent or teacher-led educational interventions increase fruit and vegetable intake.
• Some evidence that single-component interventions increase fruit intake.
• Moderate to good quality evidence that these interventions are unlikely to change weight outcomes.
• Moderate to good evidence that school-based interventions targeting children aged 2–5 years are unlikely to affect weight outcomes.

Behavioural interventions targeting screen time and physical activity:

• Moderate quality evidence that such interventions reduce recreational screen time and total energy intake in children aged 13 years and under.
• Moderate quality evidence that they increase physical activity in children aged 13 years and under.
• Some evidence of reductions in obesity-related outcomes in children, but findings were not conclusive.
• Some evidence that similar interventions increase physical activity in adults, but evidence was not conclusive.

Technical information

This evidence review updates a systematic review on obesity, diet and nutrition undertaken for the Transforming Health Improvement Implementation Programme in 2014.

This update included only secondary-level evidence in the form of systematic reviews and meta-analyses. Reviews of reviews are recognised as useful for informing decision-making and, like systematic reviews, use explicit methods to minimise bias.

Glossary

• Universal interventions are those that can be applied to an entire population, with inclusion criteria simply being that a person is part of a defined population.
• Whole system interventions are defined as population level multi-strategy interventions delivered across entire communities, comprising of system wide changes.
• Settings based interventions are those that take place within a certain defined setting such as within schools or workplaces.
• Bias : systematic (as opposed to random) deviation of the results of a study from the ‘true’ results, which is caused by the way the study is designed or conducted.
• Systematic review: a review that summarises the evidence on a clearly formulated review question according to a predefined protocol, using systematic and explicit methods to identify, select and appraise relevant studies, and to extract, analyse, collate and report their findings. It may or may not use statistical techniques, such as meta-analysis
• Secondary research: research method that involves the synthesis, analysis, and interpretation of existing data or literature previously collected by others, rather than collecting new, primary data

Stakeholders

This review was produced for the Public Health Wales Health Improvement Directorate. The review formed part of wider work to support the Welsh Government on an Obesity Prevention and Reduction Strategy.