Recent trends of body mass index distribution among school children in Sendai, Japan: Decrease of the prevalence of overweight and obesity, 2003-2009.

It was reported that the number of obese children increased during the final decades of the 20th century. However, it is unclear whether the prevalence of obesity has changed in recent years. The aim of this study was to examine trends in the body mass index (BMI) and prevalence of obesity in 6th grade primary school children (6thPS) and 3rd year junior high school students (3rdJHS) in Sendai, Japan between 2003 and 2009. BMI (kg/m(2)) was calculated and the prevalences of overweight and obesity were defined based on internationally agreed cutoff points. The mean BMI significantly decreased during the study period in all groups. In addition, the results of regression analysis revealed that significant decreases in BMI occurred in all percentiles in all groups as well. The mean prevalence rates of overweight and obese children as defined by international reference values during the observation period were 19.5% and 4.1% for boys in 6thPS, 13.6% and 2.2% for girls in 6thPS, 13.6% and 3.0% for boys in 3rdJHS and 12.2% and 1.9% for girls in 3rdJHS, respectively. There was a significant decreasing trend in the proportion of overweight and obese children from 2003 to 2009. The downward shifts of BMI might be due to effect modification in the lifestyle of children. Since we had no further data for characterization of Sendai school children and the period of this observation was only 7 years, the reasons for the change in the prevalence of obesity in this population remain speculative.: