RESUMEN
BACKGROUND: Underweight is associated with increased mortality, relative to the normal weight category. The importance of managing underweight patients has not yet been recognized seriously in South Korea, and little information is available on the prevalence of underweight and its associated risk factors. This study aims to investigate changes in the prevalence of underweight by gender and age and analyze its trend.METHODS: Data were obtained from individuals aged >20 years, from the Korean National Health and Nutrition Examination Survey between 1995 and 2015. The subjects of this study included 134,613 adults (male, 61,152; female, 73,461). The prevalence of underweight was determined as defined by the Asia-Pacific Perspective, and socioeconomic factors associated with a predisposition to underweight were analyzed using the chi-squared test and multiple logistic regression analysis.RESULTS: Among Korean adults, the age-adjusted prevalence of underweight (body mass index < 18.5 kg/m²) was 3.1% in men and 6.3% in women. Overall, a U-shaped relationship was established between the prevalence of underweight by gender and age. There was no significant difference in socioeconomic factors related to the prevalence of underweight in men and women in their twenties. The prevalence of underweight in women aged 20–59 years showed an increasing trend (P for trends < 0.05).CONCLUSION: In individuals aged 20–29 years, the prevalence of being underweight was higher in women than in men. Recently, there has been an increasing trend in the prevalence of underweight young women of reproductive age. This requires national public health attention.