Changes in BMI and prevalence of obesity and overweight in children in Liverpool, 1998-2006.

Aims: To investigate changes in mean body mass index (BMI) and prevalence of obesity between 1998 and 2006 in annual cohorts of 9-10-year-old Liverpool schoolchildren.

Methods: Stature and body mass data collected at the Liverpool SportsLinx project's fitness testing sessions were available on 26,782 (n = 13,637 boys, 13,145 girls) participants. BMI was calculated from these data.

Results: BMI z-score increased over time (p < 0.01) in both boys (z-score range = -0.22-0.14) and girls (z-score range = -0.2-0.16), with all years showing significantly higher BMI values in comparison to the first two years of the project (p < 0.01). There were no significant differences between the most recent three years of data in boys and girls. Prevalence of obesity, and obesity plus overweight increased over time. However a 'levelling off' in prevalence was observed in the most recent three years of data (2003-2006).

Conclusions: A substantial number of Liverpool schoolchildren are at risk of obesity-related illness and disease. However the most recent three cohorts' data (2003-2006) suggest that the increasing prevalence of obesity may have slowed; a positive step towards meeting the partnership agreement to halt the year-on-year increase in obesity by 2010.