Unintentional Weight Loss in Kids

There are several reasons behind a child’s unintentional weight loss, from behavioral problems to acute illnesses to chronic conditions. Weight gain generally follows a predictable course during childhood and the online Merck Manual’s article, “Eating Problems in Young Children,” recommends using a clinical growth chart to compare a kid’s stature and weight to help determine if his weight is within a healthy range 1. Nevertheless, if you ever have concerns about your child’s weight loss, consult his pediatrician.


The Mayo Clinic in the article “Unexplained Weight Loss” states that weight loss is of particular concern if a kid has lost 5 percent or more of her body weight and she is not on a physician-supervised diet 2. Because unintentional weight loss in kids is usually a symptom of an underlying problem, it’s helpful to look for other changes in your child, like mouth sores, stomach aches, fevers or hyperactivity. Be sure to mention such changes to your child’s physician.


If a child experiences unintentional weight loss, he is at risk for malnutrition, as well as growth and development problems. Scott Moses, MD, a board-certified family physician, states in the article “Failure to Thrive Red Flags” on his website, Family Practice Notebook, that unintentional weight loss in a child can also lead to heart problems and a compromised immune system, as well as problems with the liver, kidney and spleen if left untreated 3.

Potential Causes

There are several reasons as to why a child may have unexplained weight loss 2. If a child has a sore in her mouth, loose tooth or a new tooth growing in, eating may be painful. A kid who is sick with a common virus, like the cold or flu, may lose her appetite and not want to eat. When unintentional weight loss accompanies childhood cancer, the cancer cells can affect a kid’s nutrient absorption and/or the cancer treatment can make her lose her appetite 5. Digestive disorders like celiac disease, irritable bowel syndrome and inflammatory bowel disease can cause the body to overreact to certain ingredients in food, which can lead to damage to the intestinal lining and the malabsorption of nutrients 7. Endocrine disorders such as hyperthyroidism or diabetes can cause a child’s metabolism to speed up and burn more calories than she ingests.


The Merck Manual explains that a child may not eat, or purge the food that he does eat, as a form of manipulation. Depending on the frequency and severity of these actions, a pediatrician may recommend the services of a behavioral therapist. The article “Kids and Eating Disorders” on the KidsHealth website explains that children as young as 7 can suffer from eating disorders like anorexia nervosa or bulimia because of a body dysmorphic disorder, poor body image or pressure (real or perceived) to look a certain way 14. In addition to working with his pediatrician, a kid with an eating disorder should also meet with a dietitian and mental health specialist who specializes in treating children with this mental health problem.