Changes in obesity and iron deficiency between 4 and 9 years of age. Longitudinal study of childhood obesity (ELOIN)

Background Recent studies revealed that children who are overweight have a higher risk of iron deficiency, although the etiology of this relationship remains unclear. The aim of the study was to evaluate the association between changes in obesity status between 4 and 9 years of age and iron deficiency. Subjects This population-based cohort study included 1347 children from the ELOIN study, conducted in Madrid, Spain. Follow-up with physical examinations and a computer-assisted telephone interview were carried out at 4, 6 and 9 years of age, and a blood test was performed at 9 years. Methods Changes in obesity were estimated based on body mass index and waist circumference, according to the persistence or variation in obesity rates at 4, 6 and 9 years and were classified as follows: (1) Stable without obesity; (2) Remitting obesity at 9 years; (3) Incident obesity or relapse at 9 years; and (4) Stable with obesity. Iron deficiency was defined as transferrin saturation value below 16%. Odds ratios (ORs) for iron deficiency were estimated according to obesity status using logistic regression and adjusted for confounding variables, including C-reactive protein (CRP). Results The prevalence of iron deficiency in the stable general obesity (GO) and abdominal obesity (AO) groups was 38.2% and 41.2%, versus 23.6% and 23.4% in the stable without obesity groups, respectively. The ORs for iron deficiency were 1.85 (95% CI: 1.03–3.32) in the stable GO group and 2.34 (95% CI: 1.29–4.24) in the stable AO group. This association disappeared when CRP was included in the analysis. Conclusions An extended state of obesity during the first stages of life is associated with iron deficiency, and this association may be mediated by CRP. Prevention and early detection of obesity in children should be a priority to avoid a double burden of malnutrition.