Interventions for obese preschool children are missing in Germany. However, an effective and long-lasting improvement of the health behaviour seems plausible especially in this age, since the health behaviour is impressed in this age span. Therefore, we developed the outpatient one-year lifestyle intervention "Obeldicks Mini" for obese children aged 4 to <8 years and their parents based on nutrition, education, physical activity, and behaviour therapy. This intervention addressed primarily the parents. The training program was evaluated in 84 patients. In the three months before intervention, the degree of overweight significantly increased in the participants (in mean+0.12 SDS-BMI; p=0.002). Based on an intention-to-treat approach, 69% of the participants reduced their overweight, while 24% dropped out of the intervention. The mean SDS-BMI reduction was 0.46 (p<0.001) and was associated with a significant improvement of cardiovascular risk factors such as hypertension, dyslipidemia and insulin resistance. Intima-media thickness as predictive factor for later atherosclerosis decreased significantly. Even 3 years after end of intervention, the achieved weight loss sustained.