What Is The Connection Between Weight and GERD?

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It’s All About…Location. Location. Location.

To delve into this connection, I want to first make sure we have a firm understanding of the gastrointestinal tract as it pertains to gastroesophageal reflux disease (GERD).  All the parts of the body in the diagram (below) are composed of muscle, specifically a type of muscle called “smooth” muscle.  This is not due to their affinity for jazz but rather “smooth” due to its appearance. These smooth muscles are typically responsible for involuntary movements in the body.  

All muscles have a certain amount of “tone” even at rest, meaning how much they are still “flexing”. Usually the lower esophageal sphincter (LES) (see diagram) has a higher resting tone than the stomach and this is why it prevents the gastric contents (e.g. stomach acid) from entering the esophagus.  

But, in persons with GERD something causes the resting tone of the stomach to be higher than that of the LES and this allows reflux to occur and people to experience symptoms. Keep in mind that contraction and relaxation of the LES happens via the Vagus Nerve. (For more information on the Vagus Nerve see my previous articles here and here).

Studies show that obesity is an important risk factor in developing GERD (Gastroenterological Clinics of North America, 2014; Digestive Diseases and Sciences, 2008). However, it is not just overall weight that is an important factor, but where the weight is carried on the body. 

People who have increased central obesity (think apple shaped bodies) have much higher incidences of GERD and associated complications, like Barrett’s esophagus and esophageal cancer, than people with the same body mass index but who carry their weight differently. 

The question then becomes how central obesity increases the risk of GERD. As is often the case, science and medicine do not have one definitive answer, but know there are many different contributing factors. 

One known factor is that having extra weight in the middle of one’s body increases the pressure inside of the abdominal cavity. The extra weight is a physical pressure against the stomach and this increased external pressure overcomes the resting tone of the LES. It is like what happens if you squeeze a water bottle with the lid off- the stomach contents find the path of least resistance which is up through the LES into the esophagus.  

Another way that obesity increases the risk of GERD is through dysfunction of the parasympathetic nervous system. In previous articles I have discussed the role that the Vagus Nerve plays in the parasympathetic “rest and digest” process in the GI tract. Studies show that individuals with GERD have reduced parasympathetic activity and obesity causes a reduction in parasympathetic function. These same studies show that reversal of obesity corrects the parasympathetic dysfunction.  

This study (Am J Physiol Gastrointest Liver Physiol, 2021) also explores that the actual increase in fat (also known as adipose) tissue increases inflammation in the mucous membrane covering of the esophagus. These inflammatory changes cause the esophagus to be susceptible to injury from acid reflux and GERD.

In my next article I will discuss some treatment options that exist for obesity and GERD beyond conservative diet and exercise.