Childhood obesity has long been understood as a cause of or contributor to a host of other conditions, including many that used to be considered “adult” problems, such as type 2 diabetes, high blood pressure, and high cholesterol. And its mental toll can also be as damaging as the physical one, leading to low self-esteem and even depression.
One condition you wouldn’t expect to be associated with childhood obesity, however, is nutrient deficiency. But that’s just what researchers from the University of Leeds in England found when they examined records of studies conducted in more than 44 countries around the world. Their results were published in BMJ Global Health in April.
To assess the potential of childhood obesity to contribute to nutrient deficiencies, the team from Leeds combed the Ovid Medline, Ovid Embase, Scopus, and Cochrane databases for observational studies that assessed both micronutrient status (blood, serum, or plasma levels) and weight status (body mass index or other standard measurement) in children and young adults (under the age of 25) of any ethnicity and gender.
They found 83 studies following 190,443 people that covered at least one of three key nutrients—46 included information about iron status, 28 about zinc, and 27 about vitamin A. After compiling and synthesizing data from seven of those studies that were deemed suitable for meta-analysis, the researchers found an inverted U-shaped relationship between nutrition and iron deficiency. That is, both undernourished and overnourished children were more likely to be iron deficient. And the results showed no statistical difference between boys and girls. Vitamin A and zinc deficiencies, on the other hand, were only associated with undernourished children.
One possible reason for this difference, the researchers suggested, is the inflammation associated with overweight and obesity. Chronic inflammation is known to disrupt the body’s mechanisms that regulate iron absorption.
Conclusions
While inflammation-induced iron deficiency in obese adults was already recognized as a problem, this was the first study to test such an association in children. The results are cause for concern, the researchers say, because iron deficiency in children has a negative effect on brain function—including attention, concentration, and memory—and can increase the risk of conditions such as autism and ADHD.
“The relationship between undernutrition and critical micronutrients for childhood growth and development is well established, but less is known about the risk of deficiencies…in children and adolescents who are overweight or obese, making this a hidden form of malnutrition,” said doctoral researcher Xiaomian Tan, the study’s lead author.
The researchers also noted that while iron status is certainly a concern, the larger issue is that the inflammation associated with childhood obesity leads directly to such serious conditions as heart disease, diabetes, and fatty liver.
“Our research is hugely important given the high prevalence of obesity in children,” said Tan. “We hope it will lead to increased recognition of the problem by health care practitioners and improvements in clinical practice and care.”
