Lifestyle and Dietary Behaviors Are Associated with Body Mass Index in Romanian Young Adults

Background/Objectives: Overweight and obesity are increasing globally. However, structured contemporary data on lifestyle behaviors and adiposity in Romanian young adults remain limited. Therefore, this study aimed to describe dietary and lifestyle habits, BMI, and overweight/obesity prevalence in Romanian adults aged 18–30 years and to examine associations between these variables. Methods: This cross-sectional online questionnaire study included 1202 young Romanian adults. BMI was calculated from self-reported height and weight and analyzed continuously, as well as for overweight/obesity (BMI ≥25 kg/m2). Pre-specified exposures were compulsive eating, soft-drink intake, breakfast frequency, physical activity, and sleep duration. Multivariable linear regression with heteroscedasticity-consistent standard errors was used for BMI, and modified Poisson regression with robust variance was used for overweight/obesity. Composite dietary score, sex-interaction, and sensitivity analyses were also performed. Results: Mean age was 23.2 ± 3.3 years, mean BMI was 23.8 ± 4.2 kg/m2, and 32.4% of participants had overweight/obesity. Men had higher BMI and a higher prevalence of overweight/obesity than women. Compulsive eating and soft-drink intake showed dose-dependent associations with higher BMI and higher overweight/obesity prevalence. Short sleep duration (≤5 h/night) and daily breakfast consumption were associated with a higher and, respectively, lower prevalence of overweight/obesity. Physical activity showed no independent association after full adjustment, although this finding may be influenced by the use of a single self-reported item. Composite-score analyses supported the main findings. Conclusions: In Romanian young adults, compulsive eating and soft-drink intake were the most consistent behavioral correlates of adiposity, while breakfast regularity and short sleep showed threshold-type associations with overweight/obesity. These findings may inform the design of multicomponent prevention strategies, although longitudinal confirmation is needed.