Resistin has been linked to atherosclerosis and inflammatory processes in humans. Some polyphenols have been shown to downregulate resistin expression in adipocytes. The effects of olive oil phenolics on resistin are not known; therefore, we investigated the impact of olive oil consumption on serum resistin as a function of the olive oils' phenolic content. In a randomized, controlled, cross-over study 38 healthy German men aged 38+/-2 years replaced their usual consumption of raw fat during 3 periods of 3 weeks each by 25 ml of virgin, common and refined olive oil varying in phenolic content. Serum resistin, blood lipids and urine biomarkers of subjects' compliance were analysed at baseline and at the end of each intervention period. The integration of olive oil in the subjects' habitual diet led to a decrease in total cholesterol (p=0.025) and triglycerides (p=0.013) independent of the content of phenolic compounds in the oil. Serum resistin concentrations were not affected by the olive oils' phenolic content. After low phenolic olive oil consumption, a decrease in serum resistin level was observed compared to medium and high phenolic olive oil (-0.4+/-0.1 ng/ml; p=0.040). Our results suggest that olive oil consumption has only marginal beneficial effects on serum resistin levels.