By George Constantin, PhD

Obesity has become an alarming epidemic not only in the United States but across the world. It is estimated that approximately 127 million American adults are overweight, defined as having a body mass index (BMI) of between 25 kg/m2 and 29.9 kg/m2 [1]. Another 60 million people are further classified as being obese, meaning they have a BMI of more than 30 kg/m2. Even more alarming, is fact that the World Health Organization (WHO) estimates that about 700 million adults will be obese by 2015 [2]. This is equal to 10 percent of the entire worldwide population.

Obesity is more than just being extremely overweight. Along with obesity comes an increased risk of developing numerous other adverse health conditions including type 2 diabetes, high cholesterol, high blood pressure, gallstones and obstructive sleep apnea to name a few. While obesity is a risk factor in developing obstructive sleep apnea, it also may be a consequence of this ailment.  A 2009 review article published in Clinics in Chest Medicine discusses the role obesity plays in the development of obstructive sleep apnea as well as the two-way relationship between the two conditions. And a more recent one shows that weight loss can significantly improve apnea in obese people.

What Is Sleep Apnea?

obesity sleep apnea

It is estimated that approximately 24 percent of men and 15 percent of women are affected with obstructive sleep apnea [3]. A sleep-related breathing disorder, obstructive sleep apnea is characterized by recurrent upper-airway obstruction during sleep.

Airway obstruction comes in two forms: an apnea, which is a period of time where breathing stops or is severely reduced for at least 10 seconds while sleeping; and an hypopnea, which is underbreathing, meaning that breathing is shallower and slower than normal. In scientific terms, a hypopnea is a reduction of airflow of at least 30 percent with a decrease in oxygen saturation of two percent or more for at least 10 seconds [4].

What is Oxygen Saturation?

The human blood has the important role of carrying oxygen from the lungs to the rest of the body (organs and tissues). Hemoglobin, the oxygen carrier in blood, has a certain oxygen-binding capacity. Oxygen saturation measures the percentage of hemoglobin-binding sites occupied by oxygen. In healthy individuals, the oxygen saturation of the blood leaving the heart is 95 to 100 percent. In people with sleep apnea, this oxygen saturation is compromised.

Sleep apnea is typically diagnosed when a person has an apnea-hypopnea index, also commonly referred to as AHI, of five or more per hour. The AHI is calculated by dividing the number of apneas and hypopneas by the number of hours of sleep. Combining the occurrence of apneas and hypopneas provides an effective assessment of the overall severity of sleep apnea in that it includes both sleep disruptions (apneas) and oxygen desaturations (hypopneas).

Common Risk Factors for Developing Sleep Apnea

There are several risk factors for developing obstructive sleep apnea including obesity, older age, being male, nasal obstructions, genetic factors and endocrine disorders such as thyroid disease. Being postmenopausal also puts a woman at a much higher risk for developing obstructive sleep apnea compared to premenopausal women [5]. Other research also suggests that black Americans are at greater risk than white Americans [6].


The Life-Threatening Consequences of Sleep Apnea

Once a person develops obstructive sleep apnea there is an increased risk for developing several cardiovascular-related conditions. Patients with mild obstructive sleep apnea are 42 percent more likely to develop high blood pressure after four years compared to those without the condition [10]. The risk of sudden cardiac death during sleep also is 40 percent higher in people with severe obstructive sleep apnea (AHI greater than or equal to 40 per hour) than those with a mild to moderate form (AHI between 5 and 39 per hour) [11].

Obesity As A Risk Factor For OSA

Obesity is directly related to the increasing prevalence of obstructive sleep apnea in that the condition is more common in patients who are classified as having class II (BMI of between 35 and 39.9 kg/m2) or class III (BMI of more than 40 kg/m2) obesity. This is because obesity can affect the structure and function of the upper airway.

In one study, the prevalence of obstructive sleep apnea was found to be greater than 90 percent in people with a BMI of 60 kg/m2 or more [7].  Another study also found that a 10 percent weight gain causes about a 32 percent increase in the AHI of a patient and a six-fold increase in the risk of developing moderate to severe sleep apnea [8].

Additionally, visceral fat (the fat that surrounds the internal organs) appears to be an important risk factor to developing obstructive sleep apnea. In fact, one study has demonstrated a positive correlation between central obesity and indices of obstructive sleep apnea [9].

The relationship between obesity and obstructive sleep apnea is further reinforced by research showing that weight loss can help alleviate the condition. One study found that a 10 percent decrease in weight was associated with a 26 percent decrease in obstructive sleep apnea [8]. Another study also found that AHI levels significantly decreased from 61.6 apneas/hypopneas per hour to 13.4 per hour following weight loss brought about by bariatric surgery [10].

Obesity As A Consequence Of Sleep Apnea

As previously discussed, obesity can be a risk factor for obstructive sleep apnea. Is there any evidence for an inverse association? Can obstructive sleep apnea promote obesity? Research shows that obstructive sleep apnea can promote obesity in two ways.

First, obstructive sleep apnea causes sleep loss.  Studies have shown that reductions in sleep cause the body to lose control of appetite that leads to an increase in hunger, putting patients with obstructive sleep apnea at higher risk for developing obesity.

Secondly, people who suffer with obstructive sleep apnea are involved in less physical activity than those without the condition. This means they burn fewer calories than people without obstructive sleep apnea and therefore are more likely to gain weight due to a surplus of calories. Reasons why patients with obstructive sleep apnea tend to be less physically active than healthy individuals include

  • Reductions in exercise performance. One study has demonstrated that the physical work capacity of patients with obstructive sleep apnea was in fact compromised.
  • Increases in fatigue. One particular study had a number of patients with obstructive sleep apnea participate in a “maximal exercise test” which served as an objective indicator of physical fatigue. The test revealed these patients had reduced physical work capacities, which matched the participants self-reported high levels of fatigue. These results show that the poor quality of sleep associated with obstructive sleep apnea results in decreased overall energy.
  • Increases in developing depression. According to a number of studies, obstructive sleep apnea can lead to depression, which in turn impairs motivation and makes it harder for people to exercise.

If you or someone you know believes that they are affected with obstructive sleep apnea, it is extremely important to talk to your healthcare provider to determine an appropriate course of action and treatment options to reduce the severe complications associated with the condition.

About George Constantin

Having a medical science background, Matthew Constantin, Ph.D. enjoys writing articles related to weight loss, diet and nutrition. He writes reviews of best rated diets to lose weight and gives away promotional coupon codes for Nutrisystem.


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  2. World Health Organization. Available at:
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