It's well known that obesity is associated to abnormalities of cardiac autonomic nervous response as revealed by a reduction of Heart Rate Variability (HRV). Furthermore, it is associated to abnormal resting state global arousal reflected by EEG alpha rhythms. Here we tested the hypothesis of a relationship between abnormalities of autonomic nervous system and cortical EEG rhythms in obese subjects. Resting state EEG and EKG data were recorded in 15 normal-weight subjects and 15 overweight/obese subjects. Sources of Rolandic alpha and beta rhythms were computed by LORETA software. Standard HRV indexes (i.e. low-frequency, LF; high-frequency, HF) were estimated by Kubios HRV Analysis Software (MATLAB, version 2.0, Kuopio, Finland). It was found a statistically significant linear negative correlation between the power of Rolandic sources of beta power density and LF or HF across all subjects considered as a whole group (p<0.001, Pearson). The higher the source power as a sign of cortical somatomotor idling, the lower the LH or HF values as a sign of reduced cardiac autonomic nervous response. These results suggest that cortical sensorimotor EEG rhythms and cardiac autonomic nervous response are strictly related as a function of body weight in humans.