Smoking prevalence among males is conspicuously high in Asian countries including Japan. There are few prospective intervention studies on the duration of smoking cessation within regions with a high prevalence of smokers, such as Asia. We investigated the extent to which subjects continued abstaining from smoking after receiving smoking cessation support provided for all smokers in an occupational setting, regardless of their willingness to quit smoking. The subjects were 251 male workers who were smokers and had received a smoking cessation intervention in 1997 in an occupational setting. Smoking cessation rates and body mass index (BMI) at 10, 18, 30, 42, 54, and 66 months after the initial intervention were confirmed during annual health check-ups. Those who quit smoking following the intervention and continuously abstained from smoking throughout the study period were separately examined for BMI. After five years, 10.6% of the smokers continued smoking cessation. Of the abstainers who quit following the intervention, the abstinence rate decreased in the first and second year, but it stabilized at approximately 45% after the third year. High nicotine dependence and a self-reported lack of willingness to quit smoking did not lower long-term abstinence rates. Abstainers initially gained 1.55 BMI on average, but decreased the weight gain to 0.96 BMI over six years. Introducing smoking cessation support without nicotine replacement therapy is an effective long-term strategy in a healthy population with a high smoking prevalence. Abstainers maintain their smoking cessation if they refrain from smoking for three years.