What Kind of Obesity Causes Asthma?

“All kinds of obesity cause asthma,” declared Akshay Sood, MBBS, FCCP during his presentation at CHEST 2014. In the scope of synergistic epidemics, the question of what kind of obesity causes asthma is a rather relevant one.

Obesity has various phenotypes, and Sood commented that the most common depictions are the apple and pear shapes. The apple shape was designed to consider android obesity, storing fat around the abdominal region, whereas the pear shape refers to ganoid obesity, mainly storing fat around the hip and thigh regions. While these shapes are not mutually exclusive, Sood said a cohort study following French women, weight, and asthma concluded android obesity posed a higher risk for developing asthma.

According to Sood, more reasonable methods to understand obesity phenotypes were to observe the specific locations fat was deposited through sophisticated techniques as DEXA scan and CT scan.

The association between obesity and asthma is seen in both men and women, but was reported stronger in women. It was noted that while the key visceral fats were more common among males, the prevalence of metabolic activity of visceral fats is greater in females.

According to data from the national CARDIA study, “While BMI is a very good predictor for asthma, it seems that specific fat adipose may have a role to play as well. I would like to hypothesize that fat that’s closest to the airway is also the most harmful to the airway.” Sood said, “It seems to me that the farther the fat is geographically away from the lung, the less effect it might really have on the airway.”

He emphasized that BMI is a stronger predictor than the components of the metabolic syndrome. Also, truncal fat seemed to predict the dynamic of hyperinflation in asthma, but does not predict sputum.

While further research is underway, it was also noted that studies showed leg lean mass is inversely associated with current asthma in women — increased leg muscle mass could protect against developing asthma.

Sood explained, “It is important to know that in the airway both leptin and adiponectin are expressed, so they’re very relevant proteins for asthma.”

Focused on the association between asthma and adiponectin, it was found that adiponectin talked to the lung. This led to the simplified narrative that expressed, “if you have increased global adiposity, you’ll have more visceral fat, you’ll have less systemic adiponectin, so you’ll have less airway adiponectin, which would lead to increased asthma risk.”

Sood concluded, “I think it’s important to understand all this because the treatment is really about newer ways to treat obese asthmatics that goes beyond inhaled corticosteroids. We all know inhaled corticosteroids do not particularly work in cases of obese asthmatic individual as well as they do in the lean asthmatic. Additionally, weight loss is not easily achievable, so there may be newer drug targets, which may really affect the adiponectin pathway.”