Background. Serum levels of the mannose-binding lectin (MBL), which is an activator of the complement system, have been considered as a pathogenic factor in a broad range of diseases, and means of modulating MBL are therefore being evaluated. In this study we examine the effects of weight loss on MBL levels, and in continuation of this if MBL is synthesized in human adipose tissue. Methods. 36 nondiabetic obese subjects received a very low-calorie diet (VLCD) of 800 kcal/day for 8 weeks. Blood samples were collected at baseline and after VLCD. Furthermore, we measured MBL mRNA levels by the real-time RT-PCR on human adipose tissue compared to liver tissue. Results. The mean body weight was reduced from 106.3±2.6 kg to 92.8±2.4 kg, P<0.0001. Median MBL at baseline was 746 μg/L (IQR 316–1190) versus 892 μg/L (IQR 336–1511) after 8 weeks, P=0.23. No correlations were found between weight loss and changes in MBL (r=-0.098, P=0.57). MBL real-time RT-PCR showed no expression of mRNA in adipose tissue, but as expected a good expression in liver tissue was seen. Conclusions. MBL levels are not affected by weight loss and MBL is not synthesized in human adipose tissue.