ID is a common finding in cases of metabolic alterations associated with obesity
7. Several studies have reported a primary underlying pathophysiological mechanism, which is a decreased ability for duodenal iron absorption
8. For instance, Mujica-Coopman et al. (2015) identified a significant decrease in the absorption of isotope-labeled iron in obese women of childbearing age compared to their normal-weight counterparts
9. The study found that approximately 7% of women had iron dediciency anemia, while 9% had iron deficiency. Iron status was normal in 66% of women, with no differences observed across BMI categories. Although obese women had a lower percentage of iron absorption, this did not affect their iron status. Zimmermann et al. reported a similar conclusion, stating that a higher BMI is associated with decreased iron absorption. In the study, approximately 20% of women and 42% of children were found to have an iron deficiency. Iron absorption rates were not affected by iron status
10. Recently, Benotti et al. investigated the disruption of iron metabolism in obese individuals undergoing metabolic surgery
11. The International Diabetes Federation recommends bariatric surgery as a treatment and prevention option for type 2 diabetes in obese individuals
12,13. The American Diabetes Association uses the term 'metabolic surgery' to refer to the bariatric approach that aims to prevent and treat Type II Diabetes in obese individuals
14. While the terminology may be misleading, the goal is to address the metabolic syndrome through surgery. This may be due to the low-grade inflammation that characterizes obesity. A meta-analysis conducted by Cheng et al. on iron status in obese populations found that obese individuals have higher concentrations of ferritin than normal-weight individuals
15. The authors of a recent meta-analysis concluded that overweight individuals have lower concentrations of serum iron and decreased transferrin saturation percentages than non-overweight individuals. The meta-analysis also found that overweight subjects have a significantly higher risk of iron deficiency than the controls
16.
The reduction of serum Fe may be partially attributed to the chronic inflammation caused by the progression of obesity through a series of pathological mechanisms. Adipose tissue in obese individuals contains excessive amounts of macrophages and pro-inflammatory cytokine producers, as compared to those with normal weight17. Furthermore, obesity is linked to an increase in the production of adipokines in fat cells. Adipokines play a crucial role in regulating insulin resistance, inflammation, immunity, and susceptibility to viral infections18,19. Dysregulation of adipocytokine production is implicated in the development of obesity-related diseases, including diabetes mellitus, hypertension, cardiovascular disease, and hyperlipidemia. Adipocytokines and pro-inflammatory cytokines, along with free fatty acids, contribute to the development of these diseases. Concurrently, the liver accumulates lipids, resulting in non-alcoholic fatty liver disease. This further disrupts the iron balance due to increased cytokine production and insulin resistance20.
In obese patients, a decrease in BMI leads to lower Hepcidin levels, which improves iron absorption and metabolism. After a six-month weight-loss programme, the study observed these results. The intervention led to improved inflammatory markers and iron status, resulting in a decrease in BMI21. Only weight loss programmes based on a well-balanced and healthy approach improved functional iron status due to increased dietary iron absorption, decreased expression of inflammatory cytokines, and diminished insulin resistance22.
It should be noted that the treatment of iron deficiency may have an impact on obesity. Aktas et al. found that taking iron supplements to treat iron-deficiency anemia significantly reduced BMI, improved waist circumference, and decreased triglyceride levels after treatment compared to the pre-treatment period23. However, iron deficiency anemia can worsen obesity as it is associated with greater fatigue, leading to a further decrease in physical activity24. It is essential to identify and control ID in all individuals with overweight and obesity.
In literature evaluating iron deficiency in obese individuals, only objective evaluations are included. Endocrine disorders, increased inflammation, changes in blood lipid levels, and lifestyle factors have been identified as potential contributors to reduced blood iron levels. The present study found that constipation in obese individuals is also associated with lower serum iron levels. Impaired absorption in individuals with constipation suggests that reductions in intestinal function affect the absorption of iron. Slow intestinal motility increases the change in chemical structures in the absorbable form rather than increasing the absorption process. This would be useful to evaluate constipation together in the iron treatment processes to be applied in obese individuals. Even increasing intestinal motility may reduce the need for external supplements.
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