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When a child is overweight, it can be easy to point fingers at parents. But the true causes of weight gain and loss can be pretty subtle—for example, check out how your fat cells work to produce leptin and control weight. In some cases, a lack of daily physical activity, poor nutrition, and over-eating can be the culprit. As 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,” Hollier says.
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, MPP, FAAP, and 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.” The thyroid may also cause other health problems, like fatigue and depression, that can play a role in obesity.