Does being overweight cause asthma?

The following is a post originally published by me at Asthmacentral.com/asthma on September 26, 2011.

Does Obesity Cause Asthma

So much evidence links fat with asthma that some folks like to call it Fasthma.  In fact, I was recently emailed this question:   "What are your thoughts on "Fasthma" a.k.a. "Fat Asthma" or obesity related asthma?"

I recently wrote a post  Can Eating High-Fat Foods Trigger Asthma?  I wrote about a 2010 study that determined lung function was worse after eating a high-fat meal.  One theory suggests that your asthmatic immune system might recognize saturated fat as an enemy and promptly acts to rid it from your system.

This response results in an increase in markers of inflammation such as leukotrienes and hystamine, and these increase inflammation in your respiratory tract. This causes muscles lining your air passages to constrict, and thus an asthma attack is the result.

If your exposed to something that's triggering the inflammatory response often enough, this inflammation may become permanant, and thus asthma is the result.  

Experts at the Harvard School of Public Health came up with two more theories why obesity may lead to asthma: 

1. Shallow breathing
2. Hormones released from fat tissue

Breaths are shallower than normal due to fat tissue making less room for the lungs to expand. Full stomachs also puts added pressure on the diaghragm, which further restricts the ability of the lungs to expand.

This shallow breathing increases the probability inflammation will exist in the air passages of the lungs, and this causes the airways to narrow.

Inflammation in of air passages is also believed to be caused by hormones, such as leptin, released from fat tissue. Leptin is present in all asthmatics, but it is elevated in the obese.

Likewise, people that are obese are less likely to have a hormone called adiponectin, which is an anti-inflammatory hormone.

On the flipside, inactivity due to asthma may cause obesity.  It's was also interesting to learn that researchers at Kings College in London discovered that Th2 cells responsible for causing inflammation in the lungs in asthma also a protein called PMCH which is known to increase appetite. 

In another post, Alright Asthmatics! Here's Your Incentive to Get in Shape This Year, I explained several studies that concluded that excissive adipose tissue -- fat tissue -- can cause asthma.  Or in other words, these studies show that obesity causes asthma. 

Consider the following:

• A study completed by the Center for Disease Control showed that obese adults were 66 percent more likely than normal weight adults to have asthma.
• Experts at the University of South California did a study that showed obese children were 1.5 times more likely to be diagnosed with new onset asthma.
• Results from the National Health and Nutrition Examination Survey 2005-2006 showed that "Obese children were about 26 percent more likely to have allergies than children of normal weight".
• Researchers from Kaiser Permanente, Massachusetts General Hospital and Harvard Medical School, people with asthma are five times more likely to be hospitalized for asthma, have a lower quality of life, and have worse asthma control as compared to those with asthma at a normal weight.
• According to a study released in 2007 by researchers at Emory Crawford Long Hospital, obese asthmatics are more likely to have persistent or severe asthma.
• This 2005 study by experts at the Harvard School of Public Health notes that 75 percent of emergency room visits are among asthmatics that are obese.
• Researchers also found obesity to make asthma medicines work less well, and in some cases require higher doses than normally recommended.

Surely a sedentary life from a lifetime of hardluck asthma can cause obesity.  Yet the evidence appears to be overwhelming that obesity can cause asthma too.  With the rising obesity rates of late, this may be something to be concerned about.

Regardless, this is all the more reason to eat a healthy diet and exercise -- especially if you have asthma.