The Impact of Obesity and Insulin Resistance on Iron and Red Blood Cell Parameters: A Single Center, Cross-Sectional Study

Objective: Obesity and iron deficiency (ID) are the 2 most common nutritional disorders worldwide causing significant public health implications. Obesity is characterized by the presence of low-grade inflammation, which may lead to a number of diseases including insulin resistance (IR) and type 2 diabetes. Increased levels of acute-phase proteins such as C-reactive protein (CRP) have been reported in obesity-related inflammation. The aim of this study was to investigate the impact of obesity/IR on iron and red blood cell related parameters. Materials and Methods: A total of 206 patients and 45 control subjects of normal weight were included in this cross-sectional study. Venous blood samples were taken from each patient to measure hemoglobin (Hb), serum iron (Fe), iron-binding capacity (IBC), ferritin, CRP, fasting blood glucose, and fasting insulin. Body mass index (BMI) and waist-to-hip ratio (WHR) were calculated for each patient. IR was determined using the HOMA-IR formula. Results: Subjects were divided into 3 groups according to BMI. There were 152 severely obese (BMI: 42.6 +/- 10.1), 54 mildly obese (BMI: 32.4 +/- 2.1), and 45 normal-weight (BMI: 24.3 +/- 1.3) patients. Hb levels in severely obese patients and normal controls were 12.8 +/- 1.3 g/dL and 13.6 +/- 1.8 g/dL, respectively. We found decreasing Fe levels with increasing weight (14.9 +/- 6.9 mu mol/L, 13.6 +/- 6.3 mu mol/L, and 10.9 +/- 4.6 mu mol/L for normal controls and mildly and severely obese patients, respectively). Hb levels were slightly lower in patients with higher HOMA-IR values (13.1-11.5 g/dL vs. 13.2 +/- 1.2 g/dL; p=0.36). Serum iron levels were significantly higher in the group with low HOMA-IR values (13.6 +/- 5.9 mu mol/L vs. 11.6 +/- 4.9 mu mol/L; p=0.008). IBC was found to be similar in both groups (60.2 +/- 11.4 mu mol/L vs. 61.9 +/- 10.7 mu mol/L; p=0.23). Ferritin was slightly higher in patients with higher HOMA-IR values (156.1 +/- 209.5 mu mol/L vs. 145.3 +/- 131.5 mu mol/L; p=0.62). Conclusion: Elevated BMI and IR are associated with lower Fe and hemoglobin levels. These findings may be explained by the chronic inflammation of obesity and may contribute to obesity-related co-morbidities. People with IR may present with ID without anemia.