Dietary Patterns and Sociodemographic Determinants of Underweight and Excess Body Weight Among Nursing Students in Southern Thailand.

(1) Background: The double burden of malnutrition (DBM) occurs at the population level when undernutrition and overweight or obesity coexist. In this study, DBM was operationalized as BMI-defined underweight and excess body weight (EBW) within the sampled student population. (2) Objective: To identify dietary patterns and examine their associations with sociodemographic and health behavior factors among underweight and EBW nursing students in Southern Thailand. (3) Methods: This secondary analysis used cross-sectional data collected from 372 undergraduate nursing students in 2023. Dietary intake was assessed using a food frequency questionnaire; principal component analysis identified dietary patterns, and separate multivariable linear regression models examined associations with pattern scores in the underweight and EBW subgroups. (4) Results: Underweight and EBW were present in 22.0% and 26.3% of students, respectively. The snack pattern comprised milk and milk products, sweetened beverages, bakery items, desserts, pickled fruits, and snacks; the Thai dish pattern comprised rice, spicy curry, meat, entree-over-rice dishes, and vegetables; and the high-energy pattern comprised sticky rice and fried meat. Among underweight students, Thai dish scores were positively associated with year of study (p < 0.001), breakfast intake (p < 0.001), and supper intake (p = 0.008), and negatively associated with alcohol drinking (p = 0.014) and sedentary behavior (p = 0.018). Among students with EBW, snack pattern scores were higher among female students (p = 0.032) and students reporting exercise (p = 0.001) or sedentary behavior (p < 0.001), whereas Thai dish scores were associated with income (p = 0.006), dinner intake (p = 0.005), sex (p = 0.001), and supper intake (p = 0.034). Higher GPA (grade point average) was associated with lower high-energy-pattern scores in both subgroups (underweight, p = 0.018; EBW, p = 0.007). (5) Conclusion: BMI-defined underweight and EBW coexisted in this population. Dietary pattern correlates differed by nutritional status subgroup, underscoring the need for tailored nutrition and lifestyle interventions, as well as healthier university food environments.