10 Medical Reasons Your Child Might Be Overweight

Updated: Jun. 30, 2022

A child's weight isn't always the result of diet and exercise. There are some genetic, biological, and medical causes that play a role in childhood obesity, although some are more common than others.

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Why is my child overweight?

So many things can influence weight, especially in children. As they go through the growing process, their bodies change, and it’s normal for their weight to do so as well. The most common reason children are overweight or obese is from eating too many calories for the amount of play or exercise they are doing. If a change in a child’s weight is concerning, however, there might be some underlying issues unrelated to their diet, physical activity, or development. Although many of these are uncommon, even rare, here some reasons for weight gain in children that can be related to medical conditions.

Medical Reasons Your Child Is Overweight

Leptin resistance

Eboni Hollier, MD, a board-certified pediatrician practicing in Houston, Texas, explains, “Less than 5 percent of cases of obesity are thought to be due to genetic syndromes or metabolic abnormalities.” But, that doesn’t mean they don’t exist. Dr. Hollier says that leptin resistance, although especially rare in children, can be to blame. Leptin is a hormone produced in the body’s fat cells that tells the brain when you’re full and helps balance the calories you burn and fat stored in the body. In some people, the body doesn’t regulate leptin correctly, causing leptin resistance. “It is thought that when pathways including leptin (or other parts of the brain involved in this pathway) are disrupted, that obesity may be the result,” Dr. Hollier says.

Medical Reasons Your Child Is Overweight
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Although rare in children, hypothyroidism can lead to weight gain. This condition causes the thyroid gland to produce too little of the thyroid hormone, which regulates metabolism, blood pressure, energy levels, and more. According to Maria Maguire, MD, a board-certified pediatrician with the University of Maryland Community Medical Group-Pediatrics, “usually hypothyroidism by itself only causes mild weight gain, rather than true obesity or severe weight gain.” Other thyroid health problems like fatigue and depression can play a role in obesity.

Medical Reasons Your Child Is Overweight
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Your child’s medications

If your child is currently on medication for an illness or disorder and seems to be gaining weight, his or her medications could be to blame. According to Esther K. Liu, MD, chair of pediatrics for the University of Maryland Baltimore Washington Medical Center, some medications can make you feel hungrier, decrease your metabolism, or increase fluid retention, which can contribute to weight gain. The most notable medications that affect weight in children are antidepressants, anti-seizure medications, oral steroids, and some antihistamines.

Medical Reasons Your Child Is Overweight
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Unhealthy gut

If feeding your child a healthy diet filled with fruits and vegetables doesn’t seem to make an impact on their weight, an unhealthy gut microbiome could be to blame, according to Walter Gaman, MD, a family practice physician at Healthcare Associates of Texas. “[Recent findings from studies] show that if we don’t have enough healthy bacteria in our gut, especially as children, it can lead to obesity and then continue on to diabetes and other health issues,” says Dr. Gaman. “The packaged and processed foods, artificial sweeteners and colors, along with the use of antibiotics, all play a role in destroying the good bacteria and causing an overgrowth of the bad bacteria.” In some cases, changing your child’s diet to include more foods rich in prebiotics or probiotics, like Greek yogurt without additives, can help. But, other underlying issues may also cause an unhealthy gut, like undiagnosed food allergies or lactose intolerance. If your child seems to be experiencing consistent tummy problems, it’s best to get him or her evaluated by your pediatrician.

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Cushing’s syndrome

Cushing’s syndrome causes the body to produce too much cortisol, a hormone that regulates things like blood pressure and blood sugars, and it’s triggered by an improperly functioning pituitary or adrenal gland. According to Dr. Maguire, Cushing’s syndrome can slow a child’s growth while encouraging fat retention around the waist and belly. Children with the syndrome are at risk for early puberty, diabetes, and high cholesterol and blood pressure. Cushing’s syndrome is more common in adults aged 20 to 50, but it’s still rare. Only 10 to 15 new cases occur per one million people per year, and only 10 percent of those new cases are in children.

Medical Reasons Your Child Is Overweight
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Prader-Willi syndrome

Prader-Willi syndrome (PWS) is a rare genetic disorder that can affect children and is associated with behaviors leading to weight gain, like binge eating. (It occurs in about one out of every 15,000 births.) According to Nicolette D. Morris, MD and physician director of Pediatric Outpatient Care at the University of Maryland St. Joseph Medical Center, PWS is “the most common syndromic form of obesity.” She notes that doctors will look for it in infants up to two years of age who have poor or reduced muscle tone and strength (called hypotonia); if a child between two to six years of age has hypotonia and global developmental delay, PWS may be the cause. When combined with harmful eating habits, the symptoms of PWS—including developmental delays and cognitive impairment—can cause weight gain.

Medical Reasons Your Child Is Overweight

Gestational diabetes

Women with gestational diabetes, a pregnancy condition that can cause high blood sugar, may have a baby with an increased risk of high birth weight and that may carry over to childhood. Women who are pregnant should be on the lookout for potential signs of gestational diabetes. However, elevated blood sugar can cause no symptoms at all, so most women are tested for gestational diabetes in the 24th to 28th week of pregnancy. Any pregnant woman can develop gestational diabetes, although the risk is higher in women who have high blood pressure, are overweight, have a family history of type 2 diabetes, or have prediabetes, among other risk factors. Dr. Maguire notes that babies born to mothers with gestational diabetes may be between 9 and 10 pounds at birth and that “there is higher risk that children of moms with gestational diabetes will also have increased BMI and obesity.” Here are the red flags your child has Type 1 diabetes.

Medical Reasons Your Child Is Overweight
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Bottle feeding

Some research suggests that formula-feeding is linked to a relatively small elevation in risk of overweight or obesity in children. According to Dr. Maguire, “one [theory] suggests that breastfed babies have a better ability to control their intake of food, whereas formula-fed babies are fed a set amount in the bottle—although the same is true of infants fed breast milk through a bottle.”

Medical Reasons Your Child Is Overweight
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According to Dr. Maguire, childhood depression does not cause obesity, but its devastating effects could play a role in a child’s weight gain. Dr. Maguire says, “Depression is common in the U.S.—the prevalence is about 2 percent in school age children and about 5-8 percent in adolescents. However, the weight gain associated with depression is usually mild.” She explains that excessive eating and lack of desire to participate in physical activities, two common side effects, may cause weight gain. However, “the association is often the other way around—obese children may be more likely to have depression.”

Medical Reasons Your Child Is Overweight

Asthma and allergies

Asthma and allergies don’t directly cause obesity in children, but they may indirectly affect a child’s weight. “Children with asthma and allergic rhinitis have difficulty breathing which can limit their physical tolerance for exercise,” says Dr. Liu. And, oral steroids and antihistamines that can help these conditions may also contribute to weight gain. If your child’s having difficulty participating in physical activity, talk to your child’s doctor about asthma symptoms.