Underweight among adolescents in Denmark: prevalence, trends (1998-2018), and association of underweight with socioeconomic status.

The prevalence of underweight in 11- to 15-year-olds was significantly higher among girls than boys. The prevalence remained stable from 1998 to 2018. There was no significant association between SES and prevalence of underweight. It is important to elucidate the underlying causes of underweight such as malnutrition, eating disorders, eating problems, loss of appetite, chronic diseases, insufficient knowledge of nutrients effects on bodily functions, and persistent pain.