Hypothalamic obesity occurs due to damage to the hypothalamus. This damage is usually the result of tumors, brain injuries, or inherited conditions. For people with hypothalamic obesity, healthy diet and lifestyle habits don’t always help stabilize body weight.

This article will detail five of the main causes of hypothalamic obesity. We’ll also cover how the hypothalamus plays a role in balancing energy levels, metabolism, and weight.

What Is the Hypothalamus?

The hypothalamus is a structure in the brain that helps your nervous system and endocrine system work together. The endocrine system controls your hormones, chemical messengers that regulate normal body functions. When your body senses a change through your nervous system, your hypothalamus receives certain signals.

The hypothalamus then uses hormones to talk with other parts of your brain and body. The ultimate goal of the hypothalamus is to balance your body’s functions. According to Cleveland Clinic, this brain region helps regulate your:

• Hunger and thirst
• The sense of fullness when eating, known as satiety
• Blood pressure levels
• Body temperature
• Mood
• Sleep

Your hypothalamus helps control your metabolism and energy balance. The calories you eat are mainly used for energy. Extra calories are stored in the body as fat. The greater your energy expenditure, the less fat tissue you have.

Leptin is a specialized hormone with weight-regulating effects made by your fat tissue. Specifically, leptin works on the hypothalamus to control your hunger and energy balance. The more fatty tissue you have, the more leptin you make. Leptin normally sends signals to the hypothalamus to reduce hunger, but when the hypothalamus is damaged, these signals may not work properly.

How Does Hypothalamic Obesity Develop?

Hypothalamic obesity occurs after damage to the hypothalamus. Common causes of hypothalamic dysfunction include tumors, tumor treatments, and brain injuries. In other cases, genetic conditions affect the hypothalamus.

An injured hypothalamus can’t correctly send or receive signals. For example, people with hypothalamic obesity often have leptin resistance. The hormone leptin, which normally prevents hunger, doesn’t work as well with a hypothalamic injury. This means people with hypothalamic obesity have more hunger signals than their bodies need.

Signs of hypothalamic obesity include:

• Hyperphagia (extreme, uncontrollable hunger)
• Increased food intake
• Rapid and excessive weight gain, leading to a higher body mass index (BMI)
• Insomnia or altered sleep patterns
• Weight gain even when eating less food
• Exercise intolerance, which makes physical activity harder than usual

Hypothalamic damage also slows down your metabolism. This means you need fewer calories to keep your body functioning normally. However, people with hypothalamic obesity still eat more than their bodies need. The combination of overeating and a slow metabolism leads to increased body weight over time.

Researchers are also studying more about how the pituitary gland plays a role in hypothalamic obesity. This gland sits below the hypothalamus and controls how our bodies grow and develop. Examples of factors that may lead to weight gain in hypothalamic obesity include:

• Special proteins called neuropeptides that regulate energy balance, like ghrelin
• Pituitary hormone deficiencies
• Problems with sleeping patterns

What Causes Hypothalamic Obesity?

The most common cause of hypothalamic obesity is damage to the hypothalamus. The damage may happen from tumors, surgery, radiation treatments, and other injuries. This is known as acquired hypothalamic obesity. Certain genetic conditions can also affect how well the hypothalamus functions.

1. Brain Tumors

Brain tumors that develop in or near the hypothalamus can cause hypothalamic obesity. One type of tumor — called a craniopharyngioma — causes over 50 percent of hypothalamic obesity cases.

Craniopharyngioma, a type of brain tumor, causes over 50 percent of hypothalamic obesity cases.

A craniopharyngioma develops in the brain near the pituitary gland. Children who have these tumors are typically diagnosed between ages 5 and 14, although adults between 50 and 74 are also regularly diagnosed with them. Craniopharyngiomas are benign or noncancerous tumors that grow slowly. While they aren’t as aggressive as other tumors, they can cause problems. Examples include:

• Low growth-hormone levels affecting bone and muscle strength
• Delayed puberty
• Extreme tiredness and forgetfulness

The tumor may also press on the hypothalamus. Craniopharyngiomas often lead to hypothalamic obesity. Other types of brain tumors that may cause hypothalamic obesity include:

• Pituitary adenomas — Noncancerous tumors that affect the pituitary gland
• Gliomas — Cancerous (malignant) tumors made of supportive brain cells known as glial cells
• Hamartomas — Another type of noncancerous tumor found on the hypothalamus

2. Brain Surgery and Radiation Therapy

Doctors often treat brain tumors by removing them with surgery. However, there’s a chance that the hypothalamus becomes damaged during the procedure. Brain tumors and surgical treatments are a common cause of hypothalamic obesity. Studies show that people gain the most weight within one year of surgery.

Radiation therapy is a common brain cancer treatment. It uses strong beams of radiation to kill cancer cells and shrink tumors. While doctors can target the beams directly onto the tumor, some nearby tissues may become damaged.

Radiation therapy for brain cancer can damage the hypothalamus.

Radiation therapy is a treatment option for people with tumors near the hypothalamus or pituitary gland. However, it can affect hypothalamic function and cause hypothalamic obesity. One study followed people with brain tumors near the hypothalamus after they had surgery and/or radiation. Overall, obesity rates rose from 24 percent to 52 percent five years after treatment.

3. Brain Injuries

Conditions that harm the hypothalamus can lead to hypothalamic obesity. Brain injuries — including head trauma — can affect the brain’s structures. Traumatic brain injuries (TBIs) happen when a strong force damages the brain. People develop TBIs after:

• Falls
• Car accidents
• Sports injuries
• A hit on the head

Weight gain is common after certain types of brain injuries. This is because brain damage affects metabolism and hormone levels. People with TBIs also get less physical activity compared to before their accident. One study looked at 87 people diagnosed with hypothalamic obesity. It found that 3.4 percent of cases were caused by a TBI or excessive bleeding (hemorrhage).

Certain groups of people are at a higher risk of developing a TBI. According to Mayo Clinic, they include:

• Males at any age
• Children under age 4
• People ages 15 to 24
• Older adults at risk of falling and hitting their heads

4. Infections and Inflammation in the Brain

When you get sick, your immune system works hard to fight off the infection. Inflammation is important for activating immune cells and killing bacteria and viruses. Unfortunately, this response can sometimes damage healthy cells and tissues as well. In rare cases, infections and inflammation in the brain can cause hypothalamic obesity.

Researchers are also studying whether chronic low-grade inflammation in the hypothalamus might contribute to obesity. It’s important to note that most research on this topic studies animals. We’re still learning about how inflammation plays a role in hypothalamic obesity.

5. Genetic Conditions

Some genetic conditions affect how well the hypothalamus works. People with Prader-Willi syndrome often have hypothalamic obesity as well. The genetic changes that cause Prader-Willi syndrome negatively affect the hypothalamus.

One of the most common signs of Prader-Willi syndrome includes constant hunger, overeating, and weight gain. Children with this condition start showing signs early — including eating large portions often and even consuming frozen foods or garbage. Prader-Willi syndrome may eventually lead to obesity-related complications such as type 2 diabetes, sleep apnea, and high blood pressure.

Bardet-Biedl syndrome and Prader-Willi syndrome are genetic conditions that can cause hypothalamic obesity.

Another genetic condition known to cause hypothalamic obesity is Bardet-Biedl syndrome. Researchers believe Bardet-Biedl syndrome affects how the body responds to hormones that regulate hunger and energy balance, like leptin. People with Bardet-Biedle syndrome tend to keep feeling hungry even after they’ve eaten. They also have genetic changes that affect how their bodies use energy. This is why many children with Bardet-Biedl syndrome develop obesity by age 1.

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