Why Does Sleep Apnea Cause Weight Gain: 4 Reasons

There’s a strong link between obesity and sleep apnea.

Originally, it was found that obesity is a high risk factor for developing sleep apnea (1). However, we now know that people with sleep apnea tend to gain weight as well.

This forms a vicious cycle where weight gain worsens sleep apnea, which then causes more weight gain and so on.

While we don’t know all of the reasons that sleep apnea causes weight gain, we do know a part of the picture from current research.

Symptoms of Sleep Apnea That Can Lead to Weight Gain

Let’s start by taking a quick look at the symptoms and side effects of sleep apnea (2):

• Excessive daytime sleepiness
• Loud snoring
• Morning headache
• Concentration difficulties
• Mood changes (e.g. depression or irritability)
• High blood pressure
• Decreased libido

I’ll be referring back to some of these as we look at potential causes of weight gain from apnea.

Not surprisingly, some of these are also symptoms of poor sleep quality. For example, insomnia can cause high blood pressure.

How Sleep Apnea Can Cause Weight Gain

One ambitious research paper has proposed a comprehensive mechanism showing the relationship between obesity and sleep apnea (3).

Let’s take a closer look at it:

There are 5 main ways that sleep apnea appears to lead to weight gain and obesity.

1. Physical Inactivity and Poor Dietary Habits

Both physical inactivity and poor dietary habits go together in most cases.

Many of those symptoms of sleep apnea that we glanced over can lead to both these behaviors.

People are less likely to exercise or cook something healthy if they’re:

• Tired during the day
• Stressed, depressed, irritable, etc.
• Having trouble concentrating

Even having decreased libido can lead to less activity.

It’s pretty well established that if someone has less physical activity or eats a lot of junk foods (which are typically high in calories), it’s going to lead to weight gain.

2. Insulin Resistance

We know that insulin resistance typically leads to weight gain and often obesity (4).

We also know that insulin resistance is independently associated with sleep apnea (5). The degree of insulin resistance correlates to the severity of apnea.

I’m not going to go into complete details on why insulin resistance leads to weight gain because it’s quite a complex topic, but the high level is that insulin resistance:

• Makes fat burning more difficult
• Cause glucose transport to cells to decrease, leading to low energy levels
• Affects appetite regulation
• Promotes conversion of glucose to fat

In addition, insulin resistance often leads to sleep issues. That's why medication like metformin improves insomnia symptoms in people with diabetes.

3. Reduced Renal Function

There’s some evidence that sleep apnea can impair renal function.

Impaired kidney function can lead to a whole bunch of consequences, with one of them being weight gain.

However, that weight gain is typically water weight, so it’s not that important in this context, so let’s move on.

4. Systemic Inflammation

Modern research shows that chronic inflammation is a predictor of weight gain (6).

However, the exact reasons aren’t completely known at this time, because inflammation has so many effects on the hormones in your body, which all have many bodily functions.

One interesting note is that systemic inflammation typically leads to insulin resistance and leptin resistance.

Leptin is typically inversely associated with hunger (i.e. more leptin equals less appetite).

However, recent research shows that patients with sleep apnea have high levels of leptin, and yet still tend to gain weight (7). The best current hypothesis for this is leptin resistance, which is at least partially caused by inflammation.

Does CPAP Treatment Decrease Weight Gain?

If sleep apnea causes weight gain, will treating the sleep symptoms with CPAP improve weight control?

You might think so, along with many other researchers, but the latest evidence actually shows the opposite.

Studies of subjects with sleep apnea are actually slightly more likely to gain weight if being treated with continuous positive airway pressure (CPAP) (8).

That indicates that in order to break out of this vicious cycle of weight gain and sleep apnea worsening, the underlying condition needs to be treated.

In many cases, that’s simply weight gain itself. And while it’s more difficult to lose weight while experiencing sleep apnea, for all the reasons we looked at here, it’s something that needs to be done.

The good news is that as weight is lost, apnea symptoms should improve, and you get a positive reinforcement cycle instead.

References

1. Sleep Apnea and Sleep Disruption in Obese Patients
2. Obesity and Obstructive Sleep Apnea
3. Obesity and obstructive sleep apnea: Or is it OSA and obesity?
4. What causes the insulin resistance underlying obesity?
5. Obstructive Sleep Apnea Is Independently Associated with Insulin Resistance
6. Inflammation-Sensitive Plasma Proteins Are Associated With Future Weight Gain
7. Increases in leptin levels, sympathetic drive, and weight gain in obstructive sleep apnea
8. Impact of Treatment with Continuous Positive Airway Pressure (CPAP) on Weight in Obstructive Sleep Apnea