OBJECTIVE: The aim of this study is to investigate the association between five-year changes in occupational sitting and body mass index (BMI) in working adults.

METHODS: We analyzed data from The Danish Work Environment Cohort Study (2005 and 2010, n=3.482). Data on occupational sitting, weight, height and several potential confounders were self-reported. The association between change in occupational sitting (hours) (categorized as large decrease <-7.5, moderate decrease -7.5 to <-2.5, no change -2.5 to 2.5, moderate increase >2.5 to 7.5 and large increase >7.5) and change in BMI was explored by multiple linear regression analyses.

RESULTS: 43.0% men and 36.1% women had high occupational sitting time (≥25h per week) at baseline. 31.8% men and 27.2% women decreased while 30.0% men and 33.0% women increased occupational sitting. The proportion of obese (BMI≥30) increased almost 3% for both genders. BMI changed 0.13 (CI: 0.06; 0.20, p=0.0003), per category of change in occupational sitting in women, but no association was found in men.

CONCLUSION: In women, there is a positive association between five-year changes in occupational sitting and BMI.