Hypothalamic obesity refers to obesity that is caused by physical or inborn damage to the hypothalamus. The hypothalamus is part of the brain that makes hormones that control specific body functions such as sleep, body temperature, and hunger. It also makes hormones that control other organs in the body, especially the pituitary gland. The symptoms of hypothalamic obesity vary by the cause and include uncontrollable hunger, rapid, excessive weight gain, and a low metabolic rate. If the pituitary gland is involved, symptoms may include small underdeveloped testes in males and delayed puberty. This condition most often occurs because of injury to the hypothalamus due to a tumor, swelling in the brain, brain surgery, or head trauma. The diagnosis is made by physical examination and review of the symptoms. There is no cure for hypothalamic obesity. Treatment involves a combination of surgery, medications, and nutritional and lifestyle counseling. The long-term outlook for people with this condition is dependent on weight loss and management.

Signs and symptoms of hypothalamic obesity include excessive appetite, inability to feel ‘full’, and rapid weight gain. In addition, people with this condition have a low metabolic rate, decreased physical activity, and excessive daytime sleepiness. Depending on the cause, some people with this condition will have issues related to the sex hormones, such as delayed puberty and infertility. Other symptoms can include attention deficit hyperactivity disorder (ADHD), seizures, and psychiatric conditions.

Hypothalamic obesity is caused by injury to the hypothalamus. The most common cause is related to a rare non-cancerous tumor called a craniopharyngioma. When this tumor is removed, the hypothalamus can get damaged leading to the symptoms of hypothalamic obesity. Other causes for hypothalamic obesity include other rare tumors, head trauma, swelling in the brain and being born with a brain malformation. Certain genetic syndromes also include symptoms of hypothalamic obesity.

Hypothalamic obesity is usually an acquired condition and is not inherited in families. There are a few rare genetic inherited conditions that include the symptoms of hypothalamic obesity such as Bardet-Biedl syndrome and leptin deficiency. Prader-Willi syndrome also shares symptoms with hypothalamic obesity, but it is not generally inherited in families.

The diagnosis of hypothalamic obesity is made based on the symptoms which include a sudden onset of excessive hunger and weight gain after trauma or brain surgery. Testing for specific hormone levels can also help with diagnosis and guide treatment.

Many of the medications used to treat hypothalamic obesity are also used to treat type 2 diabetes. These include metformin, octreotide, and GLP1 receptor agonists. Other medications include stimulants and hormonal treatments. Nutritional and lifestyle counseling can also help with weight management.

The long-term outlook for people with hypothalamic obesity depends on the cause of the condition and how well weight can be managed. Severe obesity can lead to complications such as diabetes, heart disease, and stroke.

The number of people with hypothalamic obesity is unknown. Craniopharyngiomas, the most common cause of this condition, are very rare and occur in about 1.3 per million people.