Objective Some obese individuals have normal insulin sensitivity. It is controversial whether this phenotype is associated with increased all-cause mortality risk.
Research Design and Methods Fifteen-year all-cause mortality data were obtained through the Regional Health Registry in 2,011 out of 2,074 Caucasian middle-aged individuals of the Cremona Study, a population study on the prevalence of diabetes mellitus in Italy. Individuals were divided in four categories according to BMI (non-obese: < 30 kg/m2; obese; ≥ 30 kg/m2) and estimated insulin resistance (insulin-sensitive: HOMA-IR < 2.5; insulin-resistant ≥ 2.5).
Results Obese insulin-sensitive subjects represented 11% (95%CI: 8.1-14.5%) of the obese population. This phenotype had similar BMI, but lower waist circumference, blood pressure, fasting glucose, triglycerides and fibrinogen, and higher HDL-cholesterol than obese insulin-resistant subjects. In the fifteen-year follow-up 495 deaths (CVD: 221, cancer: 180) occurred. All-cause mortality adjusted for age and sex was higher in the obese insulin-resistant (HR: 1.40; 95% CI: 1.08-1.81; P=0.01) but not in the obese insulin-sensitive (HR: 0.99; 95% CI: 0.46-2.11; P=0.97) when compared to non-obese insulin-sensitive subjects. Also mortality for CVD and cancer was higher in the obese insulin-resistant but not in the obese insulin-sensitive when compared to non-obese insulin-sensitive subjects.
Conclusion In contrast to obese insulin-resistant subjects, metabolically healthy obese individuals are less common than previously thought, and do not show increased all-cause, cancer and CVD mortality risks in a 15-year follow-up study.
- Received April 9, 2010.
- Accepted October 4, 2010.
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