Associations Between Living Arrangements, Changes in Lifestyle and Anthropometric Traits During the First Year of University

Abstract

Introduction: The transition into university is often accompanied by lifestyle changes that can influence weight and health behaviours, with evidence highlighting increased risk of weight gain during the first academic year. While the “Freshman 15” theory, coined in the United States of America (USA), has been widely discussed, referring to an average weight gain of around 6.8 kg (15 lb) during the first year of university, findings remain inconsistent, and less is known about how different living arrangements may shape these changes. This thesis examines the associations between living arrangements, lifestyle behaviours, and anthropometric changes among first-year university students, and compares these with patterns observed in non-university peers. Methods: Two longitudinal observational studies were conducted. Study 1 followed 78 participants at baseline, three, and eight months after entering University (across one academic year), including those living at home, in private accommodation, in halls of residence (University accommodation), and non-university peers. Study 2 tracked 40 of these participants in halls, private accommodation, and at home as they transitioned to the second year. Anthropometric traits (body weight (BW), body mass index (BMI), body fat percentage (BF%), waist-to-hip ratio (WHR), and weight-for-age percentile (W/A)) were recorded. In addition, lifestyle behaviours (diet, physical activity, sleep, and stress) were assessed using questionnaires, complemented by objective assessments from the ActiGraph GT9X Link accelerometer (physical activity and sleep). Dietary intake was assessed via Intake24’s online 24-hour dietary recall tool and reassessed after excluding misreported records. Results: Most changes in weight, body composition and lifestyle behaviours occurred within groups across the academic year, with students living away from home showing the largest increases in weight, BMI and WHR. Although between-group differences were generally limited, living arrangements influenced the timing and magnitude of changes in diet, physical activity, sleep and stress, and WHR remained consistently higher among students in halls compared with those living at home or in private accommodation. Non-university participants also experienced behavioural and BF% changes, indicating that many challenges were not exclusive to university students. In the follow-up study after one year at university, similar within-group patterns persisted, suggesting that early behavioural and anthropometric changes tended to continue over time. Students who started university in halls and in private accommodation showed further increases in weight and BMI across the 12-month follow-up, while those living at home remained comparatively stable. Conclusions: These findings demonstrate that early lifestyle and body composition changes among young adults are shaped more by within-group patterns than by large differences between accommodation types. By integrating self-reported and objective measures across two longitudinal studies, this thesis provides clearer evidence on how diet, physical activity, sleep and stress evolve from university entry through the first full academic year and after one year at university. The thesis directly addressed its research objectives and answered all research questions by identifying when behavioural and anthropometric changes occur, which groups are most affected, and how living arrangements influence these trajectories over time. The results highlight areas that may benefit from future preventive efforts to support students’ health during the transition into university, such as improving food environments in halls, supporting affordable healthy eating for students living away from home, expanding access to physical activity opportunities, strengthening stress-management and sleep-support resources during this life stage.