['In several reports, C3 and C4 have been linked to diabetes and cardiovascular disease (CVD). Here, we investigate this link and the degree of C3 activation in elderly individuals.', 'In this study, C3 and C4 and the activation fragment C3a-desArg were analysed in 1016 subjects aged 70, in which blood pressure, lipid variables and fasting blood glucose were assessed.', 'C3 levels were related to all the investigated classical cardiovascular risk factors and the metabolic syndrome (BMI, waist circumference, fat distribution, blood pressure, blood glucose levels, TG) except total cholesterol and LDL cholesterol in a highly significant fashion (Spearman up to 0,5; P\xa0<\xa00·0001). C4 and C3a-desArg were associated in the same fashion but less significantly, while the ratios C4/C3 or C3a-desArg/C3 were not, indicating that the association was not directly related to complement activation. The levels C3 and to a lesser degree C4 and C3a-desArg were associated particularly with CRP, but also with E-selectin and ICAM-1. In addition, C3 and C4 levels were shown to decline significantly in 15 female subjects enrolled in a weight-reduction programme over 4\xa0months.'] Are c3 and C4 strongly related to adipose tissue variables and cardiovascular risk factors?