Having a persistent low body mass index in childhood may increase a teenager's the risk of developing anorexia nervosa -- an eating disorder causing people to obsess about weight and what they eat.
The study, published in the Journal of the American Academy of Child and Adolescent Psychiatry, also found that a persistent high BMI in childhood may be a risk factor for later development of bulimia nervosa, binge-eating disorder, and purging disorder.
"Until now, we have had very little guidance on how to identify children who might be at increased risk for developing eating disorders later in adolescence," said Zeynep Yilmaz, an assistant professor at University of North Carolina (UNC) in the US.
"By looking at growth records of thousands of children across time, we saw early warning profiles that could signal children at risk," said Yilmaz.
"Clinically, this means that pediatricians should be alert for children who fall off and stay below the growth curve throughout childhood. This could be an early warning sign of risk for anorexia nervosa," said Cynthia Bulik, a professor at UNC.
"The same holds for children who exceed and remain above the growth curve -- only their risk is increased for the other eating disorders such as bulimia nervosa and binge-eating disorder," said Bulik.
Yilmaz said that although eating disorders are psychiatric in nature, the study highlighted the need to also consider metabolic risk factors alongside psychological, sociocultural, and environmental components.
"The differences in childhood body weight of adolescents who later developed eating disorders started to emerge at a very early age -- way too early to be caused by social pressures to be thin or dieting," said Yilmaz.
"A more likely explanation is that underlying metabolic factors that are driven by genetics, could predispose these individuals to weight dysregulation," said Yilmaz.
"This aligns with our other genetic work that has highlighted a metabolic component to anorexia nervosa," she said.
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