Background Globally, the prevalence of child and adolescent overweight and obesity has increased during the preceding decades leading to childhood obesity being acknowledged as one of the most significant health hazards of the 21st century. Yet, in Finland comprehensive and up-to-date data on the prevalence of overweight and obesity among children and adolescents have been lacking. The aim of this study was to examine the prevalence of overweight and obesity among 2-16-year-old children and adolescents living in Finland in 2018. Methods The study was based on height and weight measurements taken at child welfare clinics and school health services between 5.7.2017 and 5.4.2019 (n = 375,561). The data was collected from the Register of Primary Health Care Visits. Child and adolescent overweight and obesity were defined according to international IOTF BMI criteria (age- and sex-specific BMI cut-off points corresponding to adults' cut-off points of 25 kg/m2 for overweight and 30 kg/m2 for obesity) and reported by age group and sex. Results In 2018, nearly 20% of boys and girls aged 2-16 years were classified as at least overweight while the prevalence of obesity was 5% among both sexes. The prevalence of overweight in pre-school-aged children (2-6 years) was 12% in boys and 15% in girls, in primary school-aged children (7-12 years) 23% in boys and 22% in girls and in adolescents (13-16 years) 25% in boys and 23% in girls. Conclusions In 2018, every fifth child and adolescent in Finland was classified as either overweight or obese. The prevalence of overweight and obesity appears to increase with age in both genders. Key messages Childhood and adolescent overweight and obesity were comparatively common in Finland in 2018. As overweight and obesity often persist into adulthood, multi-professional interventions targeted at prevention and early detection are essential.

Background Several potential early-life risk factors for childhood overweight and obesity have been identified. Yet results regarding early risk factors and obesity (BMI-for-age ≥30 kg/m2) at pre-school age are mixed and boys and girls have rarely been studied separately. Our aim was to study whether pre- and perinatal factors predict obesity in 5-year-old boys and girls. Methods National register data was used to identify children born in Finland between 2007 and 2014 with data available on pre- and perinatal factors as well as on height and weight at 5 years of age (n = 131,818). Multivariable logistic regression models were used to analyze sex-specific associations between pre- and perinatal factors (e.g. maternal age, parity, pre-pregnancy BMI, smoking, diabetes, delivery method, gestational-age-adjusted birth weight) and offspring obesity. Results Five percent of boys (n = 3,551) and 3% of girls (n = 1,949) had obesity. Adjusted for potential confounders, the strongest predictor of subsequent obesity at 5 years of age was severe maternal obesity (BMI ≥35 kg/m2) (boys: OR 6.5, 95% CI 5.8-7.4; girls: OR 7.5, 95% CI 6.4-8.8) followed by maternal obesity (BMI 30.0-34.9 kg/m²) (boys: OR 3.9, 95% CI 3.5-4.4; girls: OR 5.5, 95% CI 4.8-6.2) and maternal overweight (BMI 25.0-29.9 kg/m²) (boys: OR 2.3, 95% CI 2.1-2.5; girls: OR 2.6, 95% CI 2.3-3.0). Other factors associated with child obesity were maternal smoking during pregnancy (boys: OR 1.8, 95% CI 1.6-1.9; girls: OR 2.0, 95% CI 1.8-2.2) and being born large for gestational age (boys: OR 1.9, 95% CI 1.6-2.2; girls: OR 2.1, 95% CI 1.8-2.6). Conclusions These findings indicate that childhood obesity may partly originate before conception, gestation and birth. As prevention of obesity may be economically and socially more sustainable than treatment of its consequences, emphasis should be put on early interventions. Particular attention should be paid on preventing maternal overweight and obesity. Key messages Maternal obesity was the strongest predictor of child obesity at 5 years of age. Investing in maternal health from as early as before conception may help prevent offspring obesity.