Dose–Response Relationships Between Physical Activity, Dietary Behaviors, and Excess Body Weight: Identification of Behavioral Risk Patterns

Background/Objectives: Dietary behaviors and physical activity are major risk factors of excess body weight; however, less is known about behavioral risk patterns and the role of physical activity in the context of unhealthy dietary patterns. The aim of this study was to identify behavioral risk patterns and multidimensional behavioral profiles associated with overweight/obesity and excess adiposity in physically active young adults. Methods: The cross-sectional study included 418 university students (199 men and 219 women). Physical activity was assessed using the IPAQ-LF, whereas dietary behaviors were evaluated using the QEB questionnaire. Healthy (fruit–vegetable) and unhealthy (fast food–sweets) dietary indices were derived from questionnaire responses. Logistic regression, predicted probability profiling, behavioral risk mapping, response surface analyses, and decision tree models were applied to evaluate behavioral associations with BMI- and FMI-defined outcomes. Results: The unhealthy dietary index emerged as the strongest behavioral predictor of excess body weight and adiposity. Higher fast food and sweets consumption was associated with increased odds of overweight/obesity (OR = 1.70, 95% CI: 1.31–2.24) and excess fat accumulation (OR = 1.96, 95% CI: 1.36–2.83). Physical activity demonstrated a positive association with BMI-defined overweight/obesity risk (OR = 0.69, 95% CI: 0.52–0.92), although no significant interaction effects were observed between physical activity and dietary behaviors. Multidimensional analyses identified distinct behavioral risk zones, whereas decision tree models indicated that unhealthy dietary behaviors represented the dominant factor underlying obesity-related risk classification. Conclusions: Unhealthy dietary behaviors demonstrated stronger associations with excess body weight and adiposity than protective dietary behaviors related to fruit and vegetable intake. Although physical activity was generally associated with lower obesity-related risk, unhealthy dietary behaviors showed stronger associations with adverse body composition outcomes.