OBJECTIVE:Nerve traffic recordings (MSNA) have shown that sympathetic activation may occur in obese individuals (O). However, the small sample size of the available studies, presence of comorbidities, including sleep apnea, heterogeneity of the patients examined as well as presence of confounders represented major weaknesses not allowing to draw definite conclusions. This is particularly the case for overweight condition. DESIGN AND METHOD:The present metanalysis evaluated 1167 O recruited in 45 microneurographic studies. The analysis was primarily based on MSNA quantification in O of different clinical severity, excluding as concomitant conditions hypertension, sleep apnea and other comorbidities.Assessment was extended to the relationships of MSNA with other neuroadrenergic markers, such as venous plasma norepinephrine and heart rate (NE and HR, respectively), anthropometric variables, such as body mass index (BMI), waist-hip ratio (WHR) and metabolic variables. RESULTS:Compared to normoweight MSNA was significantly greater after adjustments for confounders in overweight and more so in O (37.0 ± 4.1 vs 43.2 ± 3.5 and 50.4 ± 5 bs/100 hb, P < 0.01). MSNA was directly and significantly related to BMI and WHR (r = 0.41 and r = 0.64, P < 0.04 and <0.01 respectively), clinic blood pressure (r = 0.68, P < 0.01), total cholesterol, LDL cholesterol, triglycerides and glucose (r = 0.91, 0.94, 0.80 and 0.59, respectively, P < 0.01). No significant correlation was found between anthropometric indices and plasma insulin, HOMA index and plasma leptin. No correlation was found between MSNA and HR and NE. CONCLUSIONS:Both O and overweight patients are characterized by sympathetic overactivity which mirrors the increase in BMI and WHR and the severity of the obese state and reflects metabolic alterations, with the exclusion of insulin. Neither HR nor NE appear to represent in O and in overweight faithful mirrors of the occurring sympathetic activation.