Background: The consequences of increased body mass index (BMI) on the metabolic disorders associated with metabolic syndrome (MetS) have not been thoroughly examined.
Methods: We analyzed data from 262 individuals, 97 men and 165 women (aged 18-70 years), classified with MetS to investigate whether variations in BMI could be associated with parameters of dyslipidemia, insulin resistance, or low-grade inflammation. We hypothesized that increases in BMI would positively correlate with the major dysregulations in metabolism that define MetS. For this purpose, individuals were separated into four subgroups based on their BMI: normal weight (<25 kg/m(2)), overweight (≥25 to <30 kg/m(2)), obese (≥30 to <40 kg/m(2)), and morbidly obese (≥40 kg/m(2)).
Results: As expected, body weight and waist circumference increased significantly as BMI increased (P < 0.0001). Both systolic and diastolic blood pressure were lower in the normal BMI group compared with the other three BMI groups (P = 0.001). Markers of HDL metabolism were adversely impacted in elevated BMI groups, as both high-density lipoprotein cholesterol (HDL-C) and large HDL decreased as BMI increased (P = 0.01). BMI was negatively correlated with HDL-C (r = -0.193, P = 0.002), HDL size (r = (-)0.227, P = 0.002), and large HDL (r = -0.147, P = 0.037). In addition, plasma insulin was highest in subjects classified as morbidly obese (P < 0.0001). There was also a strong positive correlation between BMI and plasma insulin (r = 0.413, P < 0.0001), whereas adiponectin, a marker of insulin sensitivity, was negatively correlated with BMI (r = -0.288, P = 0.001). Finally, BMI was positively correlated with proinflammatory C-reactive protein (r = 0.312, P = 0.0001) and interleukin-6 (r = 0.238, P = 0.001).
Conclusions: The data from this study suggest that the physiological factors associated with increased BMI exacerbate the metabolic abnormalities characteristic of MetS.