Factors associated with BMI change over five years in a Swedish adult population. Results from the Scania Public Health Cohort Study

Objectives: On account of the increasing worldwide problems associated with overweight and obesity, the aim of the present study was to examine BMI change over 5 years in relation to different lifestyle-, demographic- and psychosocial work-related factors. Methods: A cohort of 9913 persons responded to an identical survey in 2000 and 2005. BMI change over the period was examined in relation to gender, age, educational level, physical activity, job strain, and baseline BMI. Results: Mean BMI as well as prevalence of overweight and obesity increased in the cohort; most among younger persons. In all groups but younger women, BMI increase was greatest in the lowest baseline BMI quartile. Low education was associated with increased BMI at baseline, but not with BMI change over time except among young women. Exercisers had lower BMI than non-exercising persons, and exercise pattern over time was also significantly associated with BMI change. The greatest BMI increase was found among exercise drop-outs, while those who had taken up exercise during the study period were the only group who did not show a significant BMI increase over the study period. Job strain showed inconsistent associations with BMI change. Conclusions: Although socioeconomic differences in BMI were observed, these inequalities did not appear to be increasing, except among young women. Persons with a low initial BMI increased more in weight than persons with a high initial BMI. Exercise behaviour appeared to be an important factor for maintaining, or avoiding heavy increase in, BMI.