BACKGROUND: A healthy diet is important for the prevention and management of major chronic diseases including cancer, cardiovascular disease, diabetes, and obesity. However, the effect of dietary intervention-based education and consultation has not been satisfactory. This study sought to investigate the effects of a diet intervention supplying food directly to the workplace cafeteria. METHODS: Study subjects included 36 employees (23 men) staffed at two companies located in Seoul and Gyeonggi-do. Participants were supplied with liquid meals made mainly with fruits and vegetables for breakfast and dinner. Lunch was supplied as well and comprised of a balanced diet. Consumption of other foods, except water and provided snacks, were prohibited. The program also included light exercise, yoga, and mind-body control for 20 minutes, three times a week. Changes in anthropometric and metabolic parameters were evaluated. RESULTS: None of the subjects complained of serious adverse effects or dropped out of the program. Post-intervention mean body weight and body fat mass decreased significantly (-3.3 kg and -2.0 kg respectively, p<0.001 for both comparisons). There were additional reductions in systolic blood pressure (-6.7 mmHg, p<0.001), fasting glucose (-9.0 mg/dL, p<0.001), total cholesterol (-13.9 mg/dL, P=0.005), triglyceride (-44.0 mg/dL, p<0.001), and insulin (-2.4 uIU/mL, P=0.007). The satisfaction rate of the program was 88%. CONCLUSIONS: This study showed that a diet intervention supplying food directly to the workplace cafeteria could succeed in decreasing body weight and improving metabolic parameters, most likely due to high compliance.