The prevalence of childhood obesity in Wales is 12%. It has been estimated that obesity will cost the NHS £10 billion a year by 2050 (Government Office for Science 2007).

To determine important risk factors associated with childhood obesity from the data in the Welsh Health Survey 2008 to 2012.

The analysis used survey data from 11,279 children aged 4-15 years. The lifestyle variables considered as potential risk factors for obesity included: intake of sugar-sweetened drinks; unhealthy food consumption; physical activity; and currently-treated illnesses. The sociodemographic and socioeconomic factors included: sex; age; Welsh Index of Multiple Deprivation quintile; National Statistics Socio-economic Classification; and housing tenure.

A total of 1,582 (20%) children were obese. A significant association was found between obesity and having one illness – odds ratio (OR) 1.20 (95% confidence interval (CI): 1.05 to 1.38, P = 0.008) and having two or more illnesses – OR 1.50 (95% CI: 1.22 to 1.85, P < 0.001), and not meeting the physical activity recommendation – OR 1.33 (95% CI: 1.17 to 1.52, P < 0.001).

Every child should meet the physical activity recommendation and those with an illness should receive a care plan to prevent or manage obesity, although this is difficult in the time available for children in clinics and consultations.