One of the most common misconceptions is that a child must be “underweight” or visibly ill before an eating disorder becomes medically serious. That is not true. I have cared for many patients who appeared “well” on the outside but were medically compromised. A child can be struggling physically even when their weight or appearance does not raise immediate concern.
It is important for a child with an eating disorder to be evaluated by an eating disorder–informed physician. I have cared for patients who were told to “eat healthier” because their cholesterol was elevated, even though elevated cholesterol is often seen in the setting of malnutrition. I have also cared for many patients who were told they were “healthy” because their labs were normal, when in reality normal labs can be falsely reassuring in a child with an even severe eating disorder. Many patients have normal lab results even when they are very ill. Normal labs do not always mean a child is safe.
This is especially important in atypical anorexia nervosa, where a child meets the psychological and behavioral criteria for anorexia but may not appear underweight. It is well documented that adolescents with atypical anorexia can have significant medical instability, including bradycardia, hypotension, and electrolyte abnormalities. I have seen many patients with atypical anorexia develop pericardial effusions and complicated refeeding syndrome. The degree, speed, and duration of weight loss often tell us more about medical risk than a single weight or BMI number.
For families, this means that rapid weight loss, stalled growth, restrictive eating, compulsive exercise, purging, or fear-driven food avoidance should be taken seriously even when a child “doesn’t look sick.”
The heart is especially sensitive to undernutrition. When the body is not receiving enough energy, it begins to conserve what it has, and the heart often responds by slowing down. In a healthy athlete, a low resting heart rate may reflect a strong, well-conditioned heart. In an eating disorder, however, a low heart rate is not a sign of fitness. It is a sign of malnutrition and energy conservation. The difference often becomes clearer when a child stands. A malnourished body will respond with a large jump in heart rate as it struggles to maintain blood flow, while a healthy athlete’s heart rate should not rise dramatically with a simple change in position. Blood pressure may also fall, leaving a child feeling dizzy, lightheaded, weak, or unusually fatigued. Fainting can occur, but the warning signs are often more subtle. A child may become dizzy or lightheaded when standing and still minimize, explain away, or deny those symptoms, even while their vital signs show that the body is struggling to compensate.This is why a careful eating disorder medical evaluation includes more than a resting heart rate. Pericardial effusions can occur in eating disorders as a complication of malnutrition and weight suppression, likely related to starvation-associated changes such as loss of cardiac and pericardial fat, reduced myocardial mass, and low metabolic/hormonal state. These effusions are often clinically silent and can improve with nutritional rehabilitation and weight restoration, but they reflect the broader cardiovascular effects of malnutrition and should be interpreted in the context of the patient’s overall medical stability. Vital signs, orthostatic measurements, an EKG and when needed, an echocardiogram, help reveal how the heart and body are responding to undernutrition.
Eating disorders become medically dangerous not only through restriction or weight loss. Purging behaviors can also create VERY serious risk, sometimes quickly.
Purging can place quiet but significant strain on the body. Repeated vomiting, laxative misuse, diuretic misuse, or other compensatory behaviors can disrupt hydration, kidney function, and the delicate balance of electrolytes the heart depends on to beat safely. These changes can lead to low potassium and metabolic derangements which may increase the risk of weakness, dizziness, palpitations, abnormal heart rhythms, or even more serious medical complications. A child who is purging may appear outwardly well while having significant internal medical risk.
This is one of the reasons purging should always be taken seriously, even when a child “appears well”. If there is concern or evidence that a child is purging, parents should seek prompt medical guidance from a provider experienced in eating disorder care. Purging can affect the body in ways that may not be apparent from the outside, and subtle early warning signs can be missed without an eating disorder informed assessment.
Refeeding requires particular care. When nutrition is increased after a period of restriction or inadequate intake, the body’s metabolism begins to shift. As insulin levels rise during nutritional rehabilitation, intracellular electrolyte shifts can occur, sometimes leading to clinically significant drops in circulating electrolyte levels with deleterious effects. During refeeding, phosphorus, potassium, magnesium, glucose regulation, renal function, liver enzymes, fluid balance, and thiamine status all require careful consideration because abnormalities in any of these areas can contribute to medical instability.
A child can begin nutritional rehabilitation with normal labs and still develop clinically significant changes as nutrition is restored. For this reason, children at risk for refeeding complications need close monitoring. Eating disorder providers are well versed in these risks and how to monitor for these dangers.
The goal is not to delay feeding. Ongoing undernutrition is dangerous, and nutrition restoration is essential for recovery. The goal is to restore nutrition thoughtfully with the right level of medical oversight. In a concierge medical model, this means close, individualized care rather than a one-time lab review. Monitoring is individualized, with close attention to each child’s risk factors, clinical symptoms, vital signs, and targeted labs as nutrition is restored.
In children and adolescents, an eating disorder can interfere with growth, pubertal development, menstrual function, bone health, and long-term physical development. A child may not only lose weight, but also stop gaining the weight needed for healthy growth. Over time, they may fall away from their expected height or weight curve, and puberty may slow, pause, or fail to progress as expected. This is seen particularly in patients with ARFID and anorexia nervosa.
When the body does not have enough energy available, it may suppress the reproductive hormone system as a way to conserve resources. In girls, this can lead to delayed menarche, irregular periods, or loss of menstrual periods. In boys, undernutrition can also affect pubertal progression, testosterone production, growth velocity, muscle development, and bone accrual. These changes are not simply “hormonal side effects”; they are signs that the body does not have enough nutritional support for normal development.
Menstrual changes are especially important because amenorrhea can reflect hypothalamic suppression from inadequate nutrition and low energy availability. However, the presence or absence of a period does not tell the whole story. Some patients continue to menstruate despite significant medical risk, and hormonal contraception can mask whether the body is producing normal cycles on its own. For this reason, menstrual history must be interpreted alongside growth curves, weight trajectory, pubertal stage, vital signs, symptoms, nutrition, exercise, and overall medical stability.
This is why pediatric eating disorder care must be interpreted differently than adult care. A single BMI or weight does not tell the whole story. The child’s prior growth pattern, expected developmental trajectory, pubertal stage, timing of weight loss, and menstrual or pubertal history all matter. Current guidelines emphasize individualized treatment goal weight ranges based on growth charts, pubertal development, and growth trajectory rather than BMI alone. The goal is not simply weight restoration; it is restoring the nutrition needed to support growth, puberty, menstrual function, bone health, and full physiologic recovery.
Families should not wait until a child looks severely ill to seek care by an eating disorder informed physician. By the time the signs are obvious, the body is already under significant stress.
A thoughtful eating disorder medical evaluation is not just a weight check. It should include a careful review of eating patterns with an in depth nutritional assessment, weight and growth history, exercise behaviors, purging behaviors, hydration, gastrointestinal symptoms, menstrual history when applicable, medications or supplements, mental health symptoms, and safety concerns.
The physical assessment should include blind or numberless weight, heart rate, blood pressure, orthostatic vital signs, temperature, physical exam, labs, and an EKG. The goal is not to frighten families. The goal is to understand how the eating disorder is affecting the body and to determine what is needed to keep their child safe.
An eating disorder becomes medically dangerous when the body begins showing signs that it is no longer able to compensate safely. Sometimes those signs are dramatic, such as fainting, chest pain, severe dehydration, or abnormal labs. But often they are quieter: a falling heart rate, dizziness on standing, stalled growth, increasing fatigue, missed periods, cold intolerance, constipation, shrinking food variety, rapid weight loss, or a child who seems increasingly trapped by rules around food, movement, or body image.
Parents do not need to know exactly how medically serious an eating disorder is before asking for help. That is what a careful medical evaluation is for.
Families do not have to wait for a crisis before seeking thoughtful, thorough medical guidance. Early recognition matters and careful monitoring matters. And every child deserves to have their symptoms taken seriously, their medical risk assessed carefully, and their recovery supported with clarity, compassion, and expertise.
Academy for Eating Disorders. Eating Disorders: A Guide to Medical Care: Critical Points for Early Recognition and Medical Risk Management in the Care of Individuals with Eating Disorders. 4th ed. Academy for Eating Disorders; 2021.
Hornberger LL, Lane MA; American Academy of Pediatrics Committee on Adolescence. Identification and management of eating disorders in children and adolescents. Pediatrics. 2021;147(1):e2020040279. doi:10.1542/peds.2020-040279
Golden NH, Katzman DK, Sawyer SM, Ornstein RM, Rome ES, Garber AK, et al. Medical management of restrictive eating disorders in adolescents and young adults: The Society for Adolescent Health and Medicine. Journal of Adolescent Health. 2022;71(5):648-654.
Sawyer SM, Whitelaw M, Le Grange D, Yeo M, Hughes EK. Physical and psychological morbidity in adolescents with atypical anorexia nervosa. Pediatrics. 2016;137(4):e20154080.
