title: Obesity and iron deficiency: a quantitative meta-analysis.
abstract: Hypoferraemia (i.e. iron deficiency) was initially reported among obese individuals several decades ago; however, whether obesity and iron deficiency are correlated remains unclear. Here, we evaluated the putative association between obesity and iron deficiency by assessing the concentration of haematological iron markers and the risks associated with iron deficiency in both obese (including overweight) subjects and non-overweight participants. We performed a systematic search in the databases PubMed and Embase for relevant research articles published through December 2014. A total of 26 cross-sectional and case-control studies were analysed, comprising 13,393 overweight/obese individuals and 26,621 non-overweight participants. Weighted or standardized mean differences of blood iron markers and odds ratio (OR) of iron deficiency were compared between the overweight/obese participants and the non-overweight participants using a random-effects model. Compared with the non-overweight participants, the overweight/obese participants had lower serum iron concentrations (weighted mean difference [WMD]: -8.37 μg dL(-1) ; 95% confidence interval [CI]: -11.38 to -5.36 μg dL(-1) ) and lower transferrin saturation percentages (WMD: 2.34%, 95% CI: -3.29% to -1.40%). Consistent with this finding, the overweight/obese participants had a significantly increased risk of iron deficiency (OR: 1.31; 95% CI: 1.01-1.68). Moreover, subgroup analyses revealed that the method used to diagnose iron deficiency can have a critical effect on the results of the association test; specifically, we found a significant correlation between iron deficiency and obesity in studies without a ferritin-based diagnosis, but not in studies that used a ferritin-based diagnosis. Based upon these findings, we concluded that obesity is significantly associated with iron deficiency, and we recommend early monitoring and treatment of iron deficiency in overweight and obese individuals. Future longitudinal studies will help to test whether causal relationship exists between obesity and iron deficiency.
authors.affiliation: Department of Nutrition, Nutrition Discovery Innovation Center, Institute of Nutrition and Food Safety, School of Public Health, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.|Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: L
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, GA, USA.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, GA, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Department of Nutrition, Nutrition Discovery Innovation Center, Institute of Nutrition and Food Safety, School of Public Health, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: X
authors.initials: X
authors.lastname: Fang
authors.affiliation: Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, State University of New York, Buffalo, NY, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Nutrition, Nutrition Discovery Innovation Center, Institute of Nutrition and Food Safety, School of Public Health, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.|Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, Hangzhou, Zhejiang, China.|Department of Nutrition, Nutrition Discovery Innovation Institute, College of Public Health, Zhengzhou University, Zhengzhou, China.
authors.forename: F
authors.identifier: http://orcid.org/0000-0001-8730-0003
authors.initials: F
authors.lastname: Wang
mesh_terms: D018798:Anemia, Iron-Deficiency / Q000097:blood / Q000209:etiology*; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005293:Ferritins / Q000172:deficiency*; D006801:Humans; D000090463:Iron Deficiencies; D015596:Nutrition Assessment; D009765:Obesity / Q000097:blood / Q000150:complications*; D015995:Prevalence
chemical_list: D015415:Biomarkers; D005293:Ferritins
keywords: Anaemia; hypoferraemia; iron deficiency; obesity