Toddlers get slimmer while adolescents get fatter--BMI distribution in five birth cohorts from four decades in Finland.

ABSTRACT

AIM: To investigate the trends in the size of Finnish children in five birth cohorts from four decades. METHODS: This is a retrospective longitudinal growth pattern study on children representing five birth cohorts 1974, 1981, 1991, 1995 and 2001 from the city of Tampere and three rural municipalities. Growth data were collected from birth to 15 years of age, except in birth cohorts 1995 and 2001 until 12 and 5 years. Body mass index (BMI, kg/m²) was calculated. Pearson's chi-square test was used in analysis. RESULTS: The 50th percentile of BMI at birth varied between the 1970's and 2000's (boys p<0.001, girls p=0.02), with increase seen in girls. The 50th BMI percentile remained unchanged in 6-month-aged boys, whereas in girls, it varied inconsistent (p=0.04). At 1 and 2 years of age, the 15th, 50th, 85th and 95th BMI percentiles decreased (p=0.26 to <0.001). The 50th BMI percentile remained fairly constant at 5 and 7 years of age. In 12- and 15-year-old boys, the 50th, 85th and 95th percentiles of BMI showed a marked increase (p=0.01 to <0.001). In 12-year-old girls, only the 85th BMI percentile increased (p=0.03). CONCLUSIONS: During the last three decades, Finnish toddlers have become markedly slimmer. Concurrently, an opposite change has taken place in adolescent boys.