A disparity between conventional lipid and insulin resistance markers at body mass index levels greater than 34 kg/m2

OBJECTIVE: The aim of this study was to examine changes in lipid profile and markers of insulin resistance with increasing body mass index (BMI) in the range 34-77 kg/m(2). In addition we compare the lipid profiles of severely obese patients with those of the Australian community. SUBJECTS AND METHODS: A total of 572 patients (85% F, 15% M) were assessed prior to gastric restrictive surgery. Conventional lipid profiles and markers of insulin resistance were measured. Lipids were compared with the Australian National Heart Foundation 1989 study (control group). RESULT: There was no difference in mean total cholesterol levels between the obese group (5.52 mmol/l) and the control group (5.47 mmol/l). The mean total cholesterol levels in the obese group fell with increasing BMI (r = -0.13, P < 0.01). Obese subjects had elevated fasting triglyceride levels 1.96 mmol/l (control group, 1.12 mmol/l, P < 0.001), but levels did not change with increasing BMI (r = 0.0, NS). HDL-C levels were lower, 1.21 mmol/l (control group 1.44 mmol/l, P < 0.001), and decreased with increasing BMI (r = -0.20, P < 0.01). LDL-C levels were lower in obese men (3.65 mmol/l vs control group 4.17 mmol/l, P < 0.01) but not women and levels fell with increasing BMI (r = -0.15, P < 0.05). For the obese group, markers of insulin resistance (fasting plasma glucose, HbA1c, fasting plasma insulin and C-peptide) all rose significantly with increasing BMI. CONCLUSION: Raised total cholesterol is not a co-morbidity of severe obesity. There is a disparity between the conventional lipid measures and insulin resistance measures of the metabolic syndrome with increasing BMI. Conventional lipid measures may be poor indicators of dyslipidaemic risk in the severely obese.