Behavioural and environmental determinants of overweight/obesity among Malaysian young adults: a mixed methods study using the Health Belief Model

Abstract Background Obesity is a growing concern among young Malaysian adults, increasing the risk of chronic diseases. This study investigates the dietary and lifestyle risk factors of overweight/obesity (OW/OB) and explores the motivations and barriers to healthy change among individuals with OW/OB. Methods A sequential explanatory mixed-methods design was used. Phase 1 consisted of a cross-sectional survey of 280 university students (aged 18–25 years) that assessed their diet, eating behaviours, screen time, physical activity, sleep, psychosocial factors, and self-reported anthropometric measures. Multivariable logistic regression identified lifestyle and dietary predictors of OW/OB. In Phase 2, purposive sampling was used to invite 20 participants with OW/OB to four online focus group discussions guided by the Health Belief Model (HBM). Thematic analysis was conducted using NVivo, and integration occurred through a mixed-methods joint display. Results Multivariate logistic regression of Phase 1 data showed that higher cognitive restraint (AOR = 1.02, 95% CI = 1.01–1.04) and screen time (AOR = 1.05, 95% CI = 1.01–1.10) were positively associated with OW/OB, while vegetable intake was protective (AOR = 0.80, 95% CI = 0.68–0.95). Qualitative findings revealed key mechanisms underpinning these associations: cravings and restrictive eating cycles, cost and time barriers to healthy eating, digital-driven cues for sedentary snacking, and heightened perceived susceptibility to future illness. Integration of findings showed that although young adults recognise the severity of obesity, structural and psychosocial barriers often outweigh intentions to adopt healthier behaviours. Conclusion The risk of obesity among Malaysian young adults is shaped by the interaction of dietary habits, digital lifestyles, and behavioural mechanisms linked to the HBM. Effective interventions must extend beyond education to address the affordability of healthy food, manage screen-related behavioural cues, and enhance coping strategies for stress and cravings. This study provides deeper insight into modifiable pathways and supports the design of targeted obesity prevention strategies for Malaysian youth.