Targeting children aged six to 12 with school-based programmes that encourage healthy eating, physical activity and positive attitudes to body image are among a range of interventions that can help reduce levels of obesity, according to a new review of the evidence. While some people argue against taking action because they worry that the action could itself do harm, evidence of harm due to the interventions themselves was not found across the studies. “There is now compelling evidence that strategies can be implemented to halt the growing rates of obesity in children. We know that doing nothing is likely to result in increases of overweight and obesity, particularly in countries where the prevalence continues to rise”, says the lead researcher of this study, Prof Elizabeth Waters, who works at the McCaughey Centre at the University of Melbourne, Australia. The research is published in The Cochrane Library.

Childhood obesity can cause social, psychological and health problems, and is linked to obesity later in life and poor adult health.

An international team of researchers have updated a previous Cochrane Review by searching for new evidence from existing studies to see which forms of intervention could have maximum effect in helping children to avoid becoming obese. They found that since 2005 the number of trials had increased from 22 to 55. With this increased pool of information they could make a more thorough assessment of the various approaches people had taken.

Becoming obese is strongly linked to inappropriate nutrition and low levels of physical activity, so unsurprisingly many of the programmes aimed to improve either or both of these behaviours.

The studies varied in terms of what programmes they evaluated for preventing obesity and the degree of benefit they identified. Nevertheless, taken together the review indicates that the interventions had a positive impact on average bodyweight. “Our findings show that obesity prevention is worth investing in. Given the range of programmes included in this review, it is hard to say exactly which components are the best, but we think the strategies to focus on are those that seek to change environments, rather than just the behaviour of individuals,” says Waters. The evidence identifies a number of promising policies and strategies that could be considered for implementation. These include:

Including healthy eating, physical activity and body image in school curricula.

  Increasing the number of opportunities for physical activity and the development of fundamental movement skills during the school week.
  Improving the nutritional quality of food supplied in schools.
  Creating environments and cultural practices within schools that support children eating healthier foods and being active throughout each day.
  Professional development and capacity building activities which help to support teachers and other staff as they implement health promotion strategies and activities.
  Giving more attention to parent support and home activities that encourage children to be more active, eat more nutritious foods and spend less time in screen-based activities.

“Research that aims to reduce childhood obesity must now concentrate on finding ways of embedding effective interventions in health, education and care systems, so that we can make population-wide, long term impacts on the levels of obesity,” says Waters.

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1. About The Cochrane Library

The Cochrane Library contains high quality health care information, including the Cochrane Database of Systematic Reviews, from the Cochrane Collaboration. Cochrane Systematic Reviews bring together research on the effects of health care and are considered the gold standard for determining the relative effectiveness of different interventions. The Cochrane Collaboration (http://www.cochrane.org) is a UK registered international charity and the world’s leading producer of systematic reviews. It has been demonstrated that Cochrane Systematic Reviews are of comparable or better quality and are updated more often than the reviews published in print journals (Wen J et al; The reporting quality of meta-analyses improves: a random sampling study. Journal of Clinical Epidemiology 2008; 61: 770-775).

In June 2011, the Cochrane Database of Systematic Reviews received an impact factor of 6.186, from Thomson ISI, placing it in the top ten general and internal medicine journals.

The Cochrane Library is published by Wiley-Blackwell on behalf of The Cochrane Collaboration.

The Cochrane Library Podcasts: a collection of podcasts on a selection of Cochrane Reviews by authors of reviews in this issue will be available from http://www.cochrane.org/podcasts.

2. Accessing The Cochrane Library

The Cochrane Library can be accessed at http://www.thecochranelibrary.com. Guest users may access abstracts and plain language summaries for all reviews in the database, and members of the media may request full access to the contents of the Library. For further information, see contact details below. A number of countries, including countries in the World Bank’s list of low- and low-middle income economies (countries with a gross national income (GNI) per capita of less than $4700), have national provisions by which some or all of their residents are able to access The Cochrane Library for free. To find out more, please visit http://www.thecochranelibrary.com/FreeAccess.

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