Large volumes of sitting time have been associated with multiple health risks such as diabetes, heart disease and premature death. Especially, in office workers sitting time per day can accumulate to over 10 hours a day. To reduce sitting time for office workers in a Dutch insurance company, an intervention will be implemented. The intervention contains the introduction of alternative workstations, intervention sessions with an occupational physiotherapist and an activity tracker with a self-help program booklet. The goal of this study is to evaluate the (cost) effectiveness of this intervention on the short term (3 months) and long-term (12 months). The primary outcome is objectively assessed sitting time.