Low-Carbohydrate Diet and Metabolic Syndrome Risk in Korean Adults: A Korea National Health and Nutrition Examination Survey Study

Aims: Low-carbohydrate diets (LCDs) are associated with metabolic benefits, but their long-term effects remain uncertain, particularly in Asian populations with traditionally high carbohydrate intake. This study examined LCD patterns and their association with metabolic syndrome (MetS) in Korean adults using nationally representative data from the 2022–2023 Korea National Health and Nutrition Examination Survey (KNHANES). Methods: Among 9617 adults aged ≥20 years with complete dietary and health data, LCD score was calculated from the percentage of energy derived from carbohydrates (reverse-scored), fats, and proteins, and participants were categorized into high-carbohydrate, moderate-carbohydrate, and low-carbohydrate groups. MetS was defined using an Adult Treatment Panel III and Korean criteria. Survey-weighted logistic regression was applied to assess associations between LCD score and MetS across sequentially adjusted models. Results: MetS prevalence differed significantly across LCD decile groups (LCD1: 9.6%, LCD2: 5.8%, LCD3: 9.7%; p < 0.001). In a minimally adjusted model, LCD decile 3 was associated with higher odds of MetS (OR, 1.14; 95% CI: 1.02–1.27). However, this association was attenuated and became non-significant after further adjustment for key metabolic risk factors. Obesity, blood pressure, fasting glucose, triglycerides, and high-density lipoprotein cholesterol were all strongly associated with MetS (all p < 0.001), and income-related disparities were evident, with lower-income groups showing higher carbohydrate and lower fat and protein intakes. Conclusions: These findings suggest that LCD patterns are not independently associated with MetS once underlying metabolic factors are considered. Public health strategies in Korea would be emphasized by improving nutrient quality, promoting balanced macronutrient intake, and reducing socioeconomic inequalities in diet to mitigate metabolic risk among adults.