For a rare few, insatiable hunger may make it feel as if your brain is constantly whispering in your ear, telling your body that you're hungry. Often, it can feel like that voice has no "off" switch. This feeling may be caused by a rare genetic disorder of obesity.
Hunger so overwhelming it can't be tuned out
Common symptoms of rare genetic disorders of obesity
Individuals affected by rare genetic disorders of obesity can experience a range of symptoms, but two key symptoms are most common.
Severe obesity early in life
Children, from early infancy up to the age of 10, may gain far more weight than would be expected for their age. This is called early-onset obesity.
Insatiable hunger
There may be overwhelming feelings of hunger – a deep hunger that can make it difficult to think about anything else – no matter the time of day, even just after meals. Take a closer look >
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The science of hunger
Did you know hunger isn't just triggered by your stomach? It also involves your brain.
There are specific parts of your brain that control hunger by sending signals to your body, telling it when to eat and when to stop.
In rare genetic disorders of obesity, genetic variants variants Genetic variants may result in serious health problems or be “silent” with no negative health effects. interrupt these messages and hunger gets stuck in the "on" position.
How hunger works in our bodies
Our bodies need energy to function, and we get this energy from food. When functioning properly, the body has systems that balance the food you take in with the energy you need. These natural checks and balances tell us when to eat and when to stop.
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The brain-body connection
Our bodies have several processes to balance the food we take in throughout the day with the energy we need to function.
When your stomach is empty, a signal is sent to your brain. Your brain then releases a protein to kickstart your appetite.
Once your stomach is full, a different message is sent to your brain. Your brain then dials down the protein to decrease your appetite and turns up one that is an appetite suppressant.
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Making sense of the signals
There are many parts in the brain that communicate with each other to regulate hunger. One of these areas is called the melanocortin-4 receptor, or MC4R pathway. Think of it like a road carrying news and information to and from the brain.
When this pathway works the way it should, the brain receives a message that it's time to stop eating. In rare genetic disorders of obesity, part of this pathway is broken, and the body and brain can't communicate to each other properly. The brain doesn't get the message when the stomach is full and believes that the body is starving, even though there is food in the stomach.
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Learn more about some of the many different rare genetic disorders of obesity
The role of genetics
The underlying cause of rare genetic disorders of obesity can be found in genes that aren't working properly. And though the biology that explains it can get complicated, you will probably find it helpful to have a basic understanding of genetics when you speak to your doctor.
Genes
Genes are your body's instruction manual. They determine how your body grows, develops and functions.
Genes are passed down to you from your parents. While genes can determine obvious traits like eye color and hair color, they are also responsible for genetic conditions like rare genetic disorders of obesity.
We have two copies of most of our genes – one from our mother and one from our father. All of us have changes in our genes, called variants which make us unique. Not all genetic variants cause disorders, but some can.
A closer look at genetic variants
Sometimes you need two copies of a certain gene – one from your mother and one from your father – to result in disease. Other times, just one will cause disease.
Occasionally, a gene for a rare condition will be present in both the mother and the father. When they have a child, that child may inherit two copies of the disease-causing (pathogenic) variant. If the child develops symptoms of the condition, the condition is called an autosomal recessive (AR) condition. Many rare genetic disorders of obesity are passed down from the parents to their child in this AR pattern.
You can carry a gene but not be affected
If you have only one copy of the gene with a disease-causing variant, you are considered a carrier but will generally not have any symptoms of the disease.
If both parents carry the gene for a disorder, each child they conceive will have:
Genetic predisposition vs. genetic variants
While rare genetic disorders of obesity are caused by disease-causing gene variants, there are other forms of obesity that appear to run in families, but do not follow a predictable pattern or have the same early and severe symptoms.
Two ways that you can inherit obesity from your parents are:
- a genetic predisposition to obesity, or
- a genetic variant that causes obesity
Having a genetic predisposition to obesity means that you are more likely to develop obesity than people with a different genetic makeup. Although obesity may run in your family, it doesn't mean you will develop obesity. Other factors like diet, activity level, and even where you live can influence whether or not you develop obesity.
Inheriting a genetic variant that causes a rare genetic disorder of obesity is different from a genetic predisposition. If you inherit a specific gene variant, you are likely to develop obesity, even if you change your lifestyle or environment.