Change in prevalence of overweight and obesity in Finnish children - comparison between 1974 and 2001

Objective: To analyse the possible changes in the prevalence of overweight and obesity comparing birth cohorts from four different decades in Finland.

Design: A retrospective longitudinal growth study.

Methods: The subjects representing five birth cohorts: 1974 (n = 1109), 1981 (n = 987), 1991 (n = 586), 1995 (n = 856) and 2001 (n = 766) in the city of Tampere and three rural municipalities in Finland. Data included five consecutive height and weight measurements from 2 to 15 years of age. Normal weight, overweight and obesity at the time points were classified by body mass index (BMI, kg/m(2) ) according to international age- and gender-specific BMI cut-off points. The chi-square test was used to analyse the differences in the between birth cohorts.

Results: The combined prevalence of overweight and obesity decreased significantly in 2-year-old boys (p = 0.009) and girls (p = 0.002) from 1974 to 2001. Insignificant fluctuation was seen in 5- and 7-year-old children. Both the prevalence of obesity and the combined prevalence of overweight and obesity showed a significant increase in 12- (p = 0.031 and p < 0.001) and 15-year-old boys (p < 0.001 in both) from the 1970s to 2000s. In girls, the prevalence of obesity as well as the combined prevalence of overweight and obesity increased significantly in the age group of 12 years (p = 0.023), but not in that of 15 years.

Conclusions: During the last three decades, overweight and obesity have become clearly more prevalent in Finnish young adolescents. This trend has been more obvious in boys than in girls. At the same time, 2-year-old children have shown an opposite trend.