Obesity, overweight tied to iron deficiency in young people

Key takeaways:

• The risk for iron deficiency was higher in children and young adults with obesity vs. those with overweight.
• The global burden of iron deficiency “may well be underestimated” in young people, researchers noted.

Obesity and overweight were associated with an increased risk for iron deficiency in children and young adults, findings published in BMJ Global Health showed.

According to Xiaomian Tan, MSc, a PhD student at the University of Leeds in England, and colleagues, micronutrient deficiencies have traditionally been considered a form of undernutrition.

“However, increasingly, it is recognized that [micronutrient deficiencies] also occur in the context of overweight and obesity,” they wrote. “Deficiencies in iron, zinc and [vitamin A] have been observed in adults living with overweight and obesity and associated metabolic diseases.”

The risks of these three micronutrients, which are “the most frequently limiting micronutrients in children and young people, have not been collectively examined,” Tan and colleagues added.

In the systematic review and meta-analysis, the researchers examined 83 observational studies composed of 190,443 participants aged younger than 25 years from 44 countries. Among the studies, 46, 28 and 27 investigated iron, zinc and vitamin A deficiencies, respectively.

Tan and colleagues found that obesity and overweight increased the odds for iron deficiency (pooled OR = 1.51; 95% CI, 1.2-1.82), and a U-shaped relationship was observed between iron status and body weight.

The odds for iron deficiency appeared to be higher for participants with obesity (pooled OR = 1.88; 95% CI, 1.33-2.43) vs. participants with overweight (pooled OR = 1.31; 95% CI, 0.98-1.64), although “between-group differences were not statistically different, likely driven by greater heterogeneity in the overweight vs. obesity data,” according to the researchers.

Deficiencies in vitamin A or zinc were not tied to overweight and obesity and were instead “most observed in children and young people with undernutrition,” Tan and colleagues wrote.

There were a couple of study limitations, according to Tan and colleagues. Causality could not be inferred because of potential confounding, and the analyses were restricted to studies written in English.

The researchers explained that inflammation-mediated increases in hepcidin may be a potential mechanism behind the associations between iron deficiency and overweight and obesity.

“Hepcidin prevents iron absorption from the enterocytes and iron release from splenic macrophages, thereby reducing circulating iron levels overall,” they wrote, although inflammation status “was rarely adequately assessed” across the studies.

Tan and colleagues concluded that the findings suggest the global burden of iron deficiency, specifically in young people and youth with obesity or overweight, “may well be underestimated.”