Using a population approach, we investigated whether a group health education program exerted a preventive effect on checkup items at five years later. Workers turning 35 years old before the initial implementation of the program were entered in the control group (n = 422) and those turning 35 years on this date or after were entered in the intervention group (n = 206). These groups were compared using data obtained from routine health checkups at 35 and 40 years of age. In the intervention group, self-management ability prior to and after completion of the program was compared using a 2 item questionnaire based on the General Self-Efficacy Scale (GSES) and the Health Locus of Control (HLC). In males, the intervention group showed significant inhibition of increases in body mass index (BMI), systolic and diastolic blood pressure (SBP and DBP), and gamma-glutamyl transpeptidase (gamma-GTP) compared to the control group. In females, however, a similar outcome was seen for gamma-GTP only. The evaluation index of self-management ability for both GSES and HLC significantly improved among males but did not significantly change among females at five years post-completion of the program. In particular, the group with a high GSES evaluation index experienced significant inhibition of weight gain. As a population approach, adoption of this program in the workplace for males aged 35 years may have an inhibitory effect on five-year weight gain. Further, programs which improve GSES appear effective in inhibiting weight gain.