Obesity and incidence of diabetes: Effect of absence of metabolic syndrome, insulin resistance, inflammation and fatty liver

Abstract

Background and aims: Obesity is frequently associated with non-alcoholic fatty liver disease (NAFLD), insulin resistance (IR), inflammation and metabolic syndrome (MetS), all of which increase the risk of type 2 diabetes (T2DM). However, the role of these risk factors in mediating the effect of obesity remains unclear. We investigated the association between obesity and T2DM in the absence and presence of NAFLD, IR, inflammation and MetS components.

Methods: 29,836 obese subjects without diabetes were studied in a Korean health screening program. Obesity was defined by the appropriate ethnic-specific body mass index (BMI) threshold ≥25 kg/m². Hazard ratios (HRs and 95% confidence intervals, CIs) for incident T2DM were estimated for the group with no hypertension, dyslipidemia, impaired fasting glucose, fatty liver, IR, or inflammation (n = 1717), compared to the reference group, with one or more of these factors (n = 19,757).

Results: Mean (SD) age at baseline was 37 (7) years and 1200 incident cases of diabetes occurred. Crude T2D incidence was 12.6/10,000 person-years in the group without metabolic abnormality and 143/10,000 person-years in the reference group. HR (95% CIs) for incident diabetes was 0.13 (0.06, 0.33) in the group without metabolic abnormality.

Conclusions: Obese subjects without components of the metabolic syndrome, IR, fatty liver and inflammation have an approximately 11-fold lower risk of incident type 2 diabetes than obese subjects who have these risk factors. These simple factors could be used to target limited resources in high risk obese subjects in the prevention of diabetes.

Keywords: Inflammation; Insulin resistance; Metabolic syndrome; Non alcoholic fatty liver disease; Obesity; Type 2 diabetes.