Background/objectives: In overweight and obesity (OW/OB), greater total body fat predicts higher serum hepcidin (SHep) which can impair iron homeostasis and increase risk for iron deficiency (ID). However, the effect of body fat distribution on SHep and iron homeostasis is unclear. In central obesity, interleukin (IL)-6 released from visceral adipose tissue into portal blood could strongly stimulate hepatic hepcidin synthesis. Thus, our hypothesis was that higher amounts of android fat, rather than gynoid fat, would predict impaired iron metabolism in OW/OB.
Subjects/methods: In this cross-sectional study, we enrolled 117 otherwise-healthy women into two groups: normal weight; BMI < 25 (n = 36) and OW/OB; BMI ≥ 25 (n = 81); we then subdivided the OW/OB using DEXA into tertiles based on the ratio of android fat/total body fat (AF/TBF). We measured inflammation and iron status, and assessed iron absorption in two ways: by measuring erythrocyte isotope incorporation from a labeled test meal containing 6 mg 57Fe (representing dietary iron); and by measuring change in serum iron (ΔSeFe) after a 100 mg oral iron challenge (representing supplemental iron).
Results: Greater AF/TBF correlated with higher CRP, AGP, SHep, and TIBC, and lower transferrin saturation and SeFe/SHep ratio (for all, p < 0.05). Greater AF/TBF correlated with lower supplemental iron absorption (ΔSeFe) (p = 0.08) but not lower dietary iron absorption. In multiple regressions, AF/TBF positively predicted CRP (p < 0.001) and SHep (p < 0.05); a model including AF/TBF and serum ferritin as covariates explained 65% of the variance in SHep. AF/TBF negatively predicted TSAT (p < 0.05) and iron absorption (ΔSeFe) (p = 0.07). In contrast, the ratio of gynoid fat/total body fat was not significantly associated with these variables.
Conclusion: Body fat distribution affects iron metabolism: women with greater central adiposity have higher SHep, greater impairments in iron homeostasis, and reduced iron absorption from a supplemental iron dose.