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Initial findings: key points

• The National Childhood Obesity Database (NCOD) is the largest database of its kind in the world, with enormous potential as a tool both for tracking and analysing trends in childhood obesity, and for guiding evidence based interventions to tackle this major public health problem.
• The first year of data collection has been hampered by a number of practical difficulties. These have had a significant impact on data quality and seriously limit the reliability of the results for this year, as a result of which many of the figures in this report need to be treated with considerable caution.
• There is anecdotal evidence of higher rates of opting out of the measurement process among heavier children, which is supported by the findings of this analysis. This means the figures obtained from the NCOD are likely systematically to underestimate the prevalence of overweight and obesity.
• Altogether, 538,400 children in Reception Year and Year 6 were measured – approximately 48% of those eligible.
• 80% of Primary Care Trusts (PCTs) returned some data on schools in their area, but response rates (the proportion of eligible children who were measured) varied widely across England.
• Nationally, of those children measured, 12.3% of girls and 13.4% of boys in Year R were found to be overweight, and 9.2% of girls and 10.7% of boys in the same year group were found to be obese. In Year 6, 13.8% of boys and girls were overweight, and 15.4% of girls and 18.9% of boys were obese.
• The best comparison figures available (from the Health Survey for England) show higher levels of overweight and obesity, although they follow a similar pattern.
• Comparing the NCOD results for different areas shows that the higher the response rate, the higher the apparent prevalence of obesity. This suggests that as response rate increases the estimates from the data more closely approach the true prevalence for that area.
• Improving response rates is the most important challenge facing the programme, especially tackling selective opting out by children with high BMIs which will bias the results.
• Lessons learned from 2005-06 will improve the systems for 2006-07 and strengthen reporting, data uploading and data analysis.
• Analysis of the data strongly suggests that results from the 2005-06 academic year significantly underestimate the prevalence of childhood obesity. It is therefore likely that the more accurate data anticipated in 2006-07 will appear to show an increase in obesity prevalence.