Trends in Childhood Underweight in Norwegian Children: Data From Routine Child Healthcare, 2010-2022.

AIM: This study examined age- and sex-specific prevalence and trends in underweight among Norwegian children and adolescents during the pre-pandemic period from 2010 to 2019 and COVID-19 pandemic period from 2020 to 2022. METHODS: Height and weight data from 78 024 children aged 2 to 13 years in Bergen from 2010 to 2022 were obtained from public health clinic and school health service records. Underweight grades 1 to 3 were defined using the International Obesity Task Force cut-offs. Age- and sex-specific prevalence was analysed longitudinally, and trends were assessed for boys and girls across age groups using regression analyses. RESULTS: Underweight was most prevalent among 2-year-olds and declined with increasing age, more in girls than boys. Among girls, the prevalence decreased from 19.3% at age 2 years to 6.2% at age 13 years, and among boys from 13.3% to 8.6%. The interaction between sex and age was statistically significant. During the pre-pandemic period, prevalence decreased significantly among 2-year-olds. During the pandemic period, increased prevalence of underweight was observed among 8-year-old girls. CONCLUSION: Underweight remains a relevant public health concern, with clear age- and sex-specific patterns. These findings highlight the need for continued monitoring and targeted follow-up in early childhood.