Relationship between Obesity and Iron Deficiency in Healthy Adolescents

The relationship between overweight/obesity (excess of weight [EW]) and iron deficiency (ID) is not well defined. To analyze the relationship between EW and ID in healthy adolescents, assessing the contribution of new diagnostic measures of iron status and erythropoietic activity. A cross-sectional study was made of 405 healthy adolescents, 12-16 years of age. A total of 289 were normal weight (NW) and 116 were otherwise healthy EW. Epidemiological, socioeconomic, diet, BMI Z-score, CRP (C-reactive protein), hematological, iron status, and erythropoietic activity parameters were measured. Statistical tests were Student's, analysis of variance (ANOVA), Chi-square, Pearson's correlation, and odds ratio. ID prevalence in the EW group was 22.6% vs. 29.5% in the NW group (p: 0.3). Greater body weight was associated with lower reticulocyte hemoglobin content (CHr) (NW: 31.3 ± 1.7 pg vs. OW: 30.2 ± 1.7 pg, p: 0.007) and greater CRP (NW: 0.1 ± 0.2 mg/dL vs. OW: 0.2 ± 0.18 mg/dL, p < 0.001), leukocytes (NW: 6.69 ± 1.57 × 10³/L vs. OW: 7.43 ± 1.63 × 10³/L, p < 0.02), platelets (NW: 265.6 ± 58.9 × 10³/L vs. OW: 291.8 ± 54.4 × 10³/L, p < 0.002), ferritin (NW: 32.1 ± 17.9 ng/mL vs. OW: 42.8 ± 20.3 ng/mL, p: 0.01), serum transferrin receptor (sTfR) (NW: 1.39 ± 0.4 mg/L vs. OW: 1.73 ± 0.45 mg/L, p: 0.008), sTfR-F index (sTfR/log Ferritin) (NW: 1.06 ± 0.7 vs. OW: 1.33 ± 0.85, p: 0.036) and reticulocyte count (NW: 54.2 ± 18 × 10³/L vs. OW: 65.4 ± 24.2 × 10³/L, p: 0.003). A positive correlation was observed between the BMI Z-score and CRP, ferritin, sTfR, leukocytes, platelets, and reticulocyte count, and a negative one between the BMI Z-score and CHr and medium corpuscular volume. The prevalence of ID in otherwise healthy EW adolescents was no higher than in NW. The effect of obesity on iron status was low. The findings reveal the concomitant low-grade inflammation, and probably the effect of adiposity on erythropoietic activity. Specific cutoff values for ID in adolescents with OW need to be defined.