The American Society for Parenteral and Enteral Nutrition (ASPEN) / American Academy of Pediatrics (AAP) guidelines define pediatric malnutrition (undernutrition) as an imbalance between nutrient requirements and intake that results in cumulative deficits of energy, protein, or micronutrients that may negatively affect growth, development, and/or other relevant outcomes. Obesity is a form of malnutrition as well, but only undernutrition will be discussed in this topic.

Like adult malnutrition, pediatric malnutrition can occur due to inadequate nutrient intake (inadequate access to nutrients or inadequate intake despite availability, as in anorexia nervosa), increased nutritional demands that outstrip intake (infection, congenital heart disease, cancer, traumatic injury and burns, other etiologies for inflammation), inadequate or impaired bowel absorption and transport of various etiologies, and altered nutrient utilization by the body.

In the developed setting, pediatric malnutrition is most commonly related to disease, chronic conditions, trauma, burns, or surgery, all of which are considered collectively as "illness-related malnutrition." Environmental enteric dysfunction (EED) is an enigmatic disorder of the small intestine that may have a role in pediatric malnutrition. It is associated with malabsorption, increased intestinal permeability, and chronic inflammation of the small intestinal mucosa. Malnutrition can also be due to nonillness-related etiologies, such as environmental factors, that can also negatively affect its remediation (socioeconomic conditions impacting availability of food) or to behavioral disorders such as food aversion or anorexia.

The prevalence of illness-related malnutrition in hospitalized children is reported to be between 6% and 51%, but it is widely considered to be underreported.

Multiple international studies attribute the majority of all childhood deaths to undernutrition.

No single parameter is definitive for pediatric malnutrition. Consensus guidelines from ASPEN and the AAP define malnutrition as acute (fewer than 3 months duration) or chronic (3 months or greater duration). Chronic malnutrition may result in growth deficits and particularly diminished height velocity (stunting). Severity of malnutrition is determined by z-scores of individual anthropometric variables in relation to population standards. Such measurements include height, weight, body mass index (BMI), and mid-upper arm circumference (MUAC) as well as head circumference in children younger than 2 years. Populations standards are provided by 2006 World Health Organization (WHO) charts for children younger than 2 years and by the Centers for Disease Control and Prevention (CDC) 2000 charts for children between 2 and 20 years of age.

Measurements should be tracked over time, with a reduction of z-score > 1 indicating faltering growth and warranting further investigation into the etiology of malnutrition. (See Best Tests for z-score classification values.) Management is in part dependent on the underlying etiology.

Specific deficiencies of or impaired utilization of specific micronutrients are also considered malnutrition but are addressed individually and are not within the scope of this topic.

Related topics: Protein-energy malnutrition, kwashiorkor, marasmus, bulimia, malabsorption syndrome, failure to thrive and neglect, vitamin and mineral deficiencies (vitamin A, vitamin B2, vitamin B6, vitamin B12, niacin, vitamin C, vitamin D, vitamin E, vitamin K, thiamine, folate, copper, iodine, zinc [acquired and hereditary], and iron)