The prevalence of obesity has increased at an epidemic rate, and obesity has become one of the most common health concerns in the United States. A few small studies have noted a possible association between iron deficiency and obesity.
To investigate the association between weight status, as measured by body mass index (BMI), and iron deficiency in a nationally representative sample of children and adolescents.
National Health and Nutrition Examination Survey III (1988-1994) provides cross-sectional data on children 2 to 16 years of age. Recorded measures of iron status included transferrin saturation, free erythrocyte protoporphyrin levels, and serum ferritin levels. Children were considered iron-deficient if any 2 of these values were abnormal for age and gender. With the use of age- and gender-specific BMI percentiles, at risk for overweight was defined as a BMI of > or =85th percentile and <95th percentile, and overweight was defined as a BMI of > or =95th percentile. The prevalence of iron deficiency was compared across weight groups. Logistic regression was used to estimate the association between iron status and overweight, controlling for age, gender, ethnicity, poverty status, and parental education level.
In this sample of 9698 children, 13.7% were at risk for overweight and 10.2% were overweight. Iron deficiency was most prevalent among 12- to 16-year-old subjects (4.7%), followed by 2- to 5-year-old subjects (2.3%) and then 6- to 11-year-old subjects (1.8%). Overweight 2- to 5-year-old subjects (6.2%) and overweight 12- to 16-year-old subjects (9.1%) demonstrated the highest prevalences of iron deficiency. Overall, the prevalence of iron deficiency increased as BMI increased from normal weight to at risk for overweight to overweight (2.1%, 5.3%, and 5.5%, respectively), and iron deficiency was particularly common among adolescents (3.5%, 7.2%, and 9.1%, respectively). In a multivariate regression analysis, children who were at risk for overweight and children who were overweight were approximately twice as likely to be iron-deficient (odds ratio: 2.0; 95% confidence interval: 1.2-3.5; and odds ratio: 2.3; 95% confidence interval: 1.4-3.9; respectively) as were those who were not overweight.
In this national sample, overweight children demonstrated an increased prevalence of iron deficiency. Given the increasing numbers of overweight children and the known morbidities of iron deficiency, these findings suggest that guidelines for screening for iron deficiency may need to be modified to include children with elevated BMI.