Background Overweight and obesity were recently associated with a poor prognosis in patients with autosomal dominant polycystic kidney disease (ADPKD). Whether the metabolic consequences of obesity as defined by the metabolic syndrome (MS) are also linked with disease progression remains untested. Methods Eligible ADPKD patients with different stages of CKD (n = 105) and 105 non-diabetic controls matched for CKD stage were enrolled in the study. Groups were evaluated at baseline for presence of MS, blood markers of metabolism, homeostasis model assessment of insulin resistance (HOMA-IR) score, and biochemical markers of inflammation (hs-CRP, IL-1 beta, IL-6, TNF-alpha and PON-1). MS was defined according to the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP III). Patients were followed for 12 months and progression defined as a decrease in baseline eGFR > 10%. Results MS and hypertension were more prevalent amongst ADPKD patients than in the control group. Meanwhile, markers of inflammation such as hs-CRP (3.63 [3.45-5.17] vs. 4.2 [3.45-8.99] mg/dL; p = 0.014), IL-6 (21.65 [14.1-27.49] vs. 24.9 [16.23-39.4] pg/mL; p = 0.004) and IL-1 beta (21.33 [15.8-26.4] vs. 26.78 [18.22-35] pg/mL; p < 0.001) levels were all more elevated in ADPKD patients than in non-diabetic CKD subjects. In multivariate analysis having a truncating PKD1 mutation predicted (OR 1.25 [1.09-1.43]; p = 0.002) fulfilling the MS criteria. Finally, ADPKD patients fulfilling MS criteria had a significantly more rapid progression during 12 months of follow-up than did those that did not (OR 3.28 [1.09-9.87]; p = 0.035). Conclusions Our data supports the notion that dysmetabolisms part of the ADPKD phenotype and associated with a poor outcome, especially in patients with a truncating PKD1 mutation.