This study aimed to determine the association between consumption of ultra-processed foods and obesity among Korean adults. We used the data of 7364 participants (men 3219, women 4145) aged 19–64 years from the Korea National Health and Nutrition Examination Survey (KNHANES), 2016–2018. Food items were classified using the NOVA food classification system, depending on the extent and purpose of food processing: (1) unprocessed or minimally processed foods, (2) processed culinary ingredients, (3) processed foods, and (4) ultra-processed foods. Consumption of ultra-processed foods accounted for 26.8% of the total energy intake. After adjusting for potential confounders including sociodemographic and lifestyle characteristics, subjects with the highest consumption of ultra-processed foods (fourth quartile of % energy intake from ultra-processed foods) had 0.61 kg/m2 higher body mass index (BMI; 95% confidence interval [CI] 0.23–0.99, p-trend 0.0047), 1.34 cm higher waist circumference (WC; 95% CI 0.35–2.34, p-trend 0.0146), 51% higher odds of being obese (BMI >25 kg/m2; odds ratio [OR] 1.51, 95% CI 1.14–1.99, p-trend 0.0037), and 64% higher odds of abdominal obesity (men: WC ≥90 cm, women: WC ≥85 cm; OR 1.64, 95% CI 1.24–2.16, p-trend 0.0004) than those with the lowest consumption (first quartile) among women. However, no association was found in men. These findings provide evidence that high consumption of ultra-processed foods is positively associated with obesity in Korean women. Further studies with a large-scale cohort or intervention trial are needed to identify the mechanism of associations between consumption of ultra-processed foods and health-related outcomes including obesity in Korea.

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