In an earlier study, we found a similar frequency of individuals with an abnormal correlation between serum leptin levels and body mass index (BMI) (outliers above or below the 95% confidence interval in the regression line) during treatment with antipsychotic drugs (n=301), other psychotropic drugs (n=65), and drug-free individuals (n=229). In this secondary analysis, we compare the frequency of the metabolic syndrome (International Diabetes Federation), its constituting variables, obesity, (BMI>30 kg/m2), leptin and insulin serum levels, and an insulin-resistance index (homeostatic model assessment-insulin resistance) in outliers, nonoutliers distributed in their original treatment groups, and all the nonoutliers controlled by age, sex, and BMI. We identified 28 outliers, 24 above and four below the 95% confidence interval limits. Nine individuals were under antipsychotic treatment, four under other drug treatment, and 15 were drug-free. The outliers had a significantly higher frequency of metabolic syndrome and obesity, and higher values of waist circumference, triglycerides, insulin, and blood diastolic pressure. The outliers in the correlation between leptin and BMI may represent a population at high risk of metabolic dysfunction, irrespective of the specific psychotropic drug treatment administered.