Abstract Purpose Occupational health programmes have been successfully implemented to improve body composition, physical fitness and cardiovascular risk. However, most programmes have been small and have not included long-term evaluation. Therefore, we evaluated a twelve-month life-style change programme in a German refinery. Methods We offered a supervised six-week endurance exercise programme (2 × 90 min/week), starting after a two-day life-style seminar. After the active intervention and a half-day refresher seminar, employees were encouraged to continue exercising over one year on their own, with monthly supervised sessions to maintain adherence. Anthropometry, bicycle ergometry, cardio-metabolic risk profile, inflammatory parameters, and vascular function e.g. endothelial function was studied at baseline, after three and after twelve months. Results Of 550 employees, n = 327 (age 40.8 ± 9.7 years, 88% males) participated in the study. Twelve-month intervention was associated with a reduced waist circumference (92.6 ± 12.2 to 90.8 ± 11.7 cm, 95% confidence interval for the mean change (CI): -2.5 to -1.1 cm) and a gain in maximal exercise capacity (202 ± 39.6 to 210 ± 38.9 Watt; 95% CI: + 5.1 to + 10.9 Watt). Metabolic and inflammatory parameters likewise HbA_1c and C-reactive protein improved in central tendency at a local 95% level of confidence. Vascular function e.g. Reactive-Hyperaemia-Index revealed a slight reduction, whereas no statistically robust changes in mean Cardio-Ankle-Vascular-Index and mean Ankle-Brachial-Index were observed. Conclusion Health education added by a six-week supervised exercise programme was associated with minor long-term twelve-month improvements of body composition as well as physical fitness and a concomitant improvement of inflammatory state. These changes were, however, not clinically relevant and not accompanied by statistically robust improvements of vascular function. Trial registration ClinTrialsGov: NCT01919632; date of registration: August 9, 2013; retrospectively registered.