Weight changes in young adults: a mixed-methods study

OBJECTIVE: In both the United States and United Kingdom, countries with high prevalence of obesity, weight gain is particularly rapid in young adulthood and especially identified among first-year students. DESIGN: A triangulation protocol was used, incorporating quantitative and qualitative research methods. A 27-question online survey was sent to all first-year undergraduates twice, with a 9-month interval. An online focus group was conducted at the end of the year, analysed by content and thematically. Self-reported weights and heights were validated against objectively measured data. RESULTS: From a total of 3010 first-year students, 1440 (female = 734) responded at baseline mean (s.d.) age 20 (3.6) years, body mass index 22.3 (4.6) kg m(-2), 17% smokers and 80% alcohol drinkers. At follow-up, 1275 students reported a mean weight change of 1.8 (s.d. 2.6) kg over the 9-month period. Self-reported data correlated strongly with measured weights (r = 0.999, P < 0.001) and heights (r = 0.998, P < 0.001). Predictors of weight gain were baseline weight (P < 0.001). Dairy products consumption was associated with less weight gain (P < 0.001). Fruit and vegetable consumption, and time spent on physical activity or sleeping were associated with neither weight gain nor weight loss. Focus group content analysis revealed weight gain as a major concern, reported by half the participants, and increased alcohol consumption was considered the most common lifestyle change behind weight gain. Thematic analysis identified three main themes as barriers to or facilitators of healthy lifestyles and weight; budget, peer influence and time management. CONCLUSIONS: Rapid weight gain is of concern to young adults. Students living away from home are at particular risk, owing to specific obesogenic behaviours. Consumption of fruit and vegetables, and physical activity, despite popular beliefs, were not associated with protection against weight gain.