Continuous positive airway pressure (CPAP) therapy is a common and effective treatment for obstructive sleep apnea (OSA), a condition characterized by repeated pauses in breathing during sleep. While CPAP therapy offers numerous benefits, including improved sleep quality, reduced snoring, and decreased blood pressure, many individuals prescribed CPAP machines wonder about its potential effects on their body weight. This article explores the complex relationship between CPAP use and weight loss, examining the existing research, potential mechanisms, and practical considerations.
The Link Between Sleep Apnea and Weight
A higher body weight is often associated with the most common type of sleep apnea, called obstructive sleep apnea (OSA). For this reason, some researchers have suggested that treating OSA with a CPAP machine may lead to weight loss after a person with OSA begins CPAP treatment. However, the relationship between CPAP and weight is not straightforward.
CPAP and Weight Loss: The Initial Theory
The idea that CPAP therapy could lead to weight loss stemmed from the theory that improved oxygen flow and reduced daytime sleepiness would encourage increased physical activity. Experts believed that as people felt more energized, they would be more inclined to engage in regular fitness routines. Additionally, some experts proposed that CPAP machine use could lead to weight loss through improved appetite control. Research has suggested that poor sleep can contribute to hunger and cravings, meaning that better sleep quality could lead to better appetite control.
Conflicting Research Findings
Despite the initial theory, research on the outcomes of CPAP use in weight loss has yielded conflicting results. Several small studies have produced inconsistent findings or involved very small participant groups.
In 2013, a large-scale prospective, randomized, double-blind sham-controlled clinical trial revealed that weight gain from CPAP is more likely than weight loss. This study is often cited as a landmark in the debate about CPAP machines and weight changes, as it found that individuals were more likely to gain weight with CPAP use, and that weight gain increased with longer CPAP usage. Since that time, other large-scale research has produced similar results. A meta-analysis of more than 3,000 people in 2015 confirmed a link between CPAP and increased body mass index and weight gain.
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CPAP and Weight Gain: Potential Mechanisms
Researchers are not entirely sure why treating OSA with a CPAP machine can lead to weight gain. Identifying how CPAP use affects weight is difficult because so many factors impact body weight, like diet, physical activity, hormones, and other environmental factors. For these reasons, studying the impact of CPAP on weight is challenging and research is limited. However, some potential mechanisms have been proposed:
- Changes in energy usage: Untreated OSA may cause people to use more energy as they sleep, either due to low oxygen levels or an overactive nervous system. Studies have also found that the basal metabolic rate drops after starting CPAP, which means people burn fewer overall resting calories.
- Having high blood sugar: Weight gain after CPAP use appears to happen more commonly among people who already had existing issues with the regulation of blood sugar, such as those with diabetes.
- Increases in waist sizes with CPAP use: This is not a measure of weight per se, but doctors sometimes use waist size to determine if a person has obesity.
- Time spent using CPAP machine: Weight changes may depend on how much time people spend using CPAP nightly. One analysis found that weight gain only happened in those who used their CPAP machine for less than five hours per night. But, another showed that those who use a CPAP for over four hours per night tend to gain more weight.
- Decreased resting metabolic rate: A 2016 systemic review indicated that CPAP use may decrease your resting and sleeping metabolic rate. Because it takes your body out of a state of active stress at night, CPAP may inadvertently decrease your resting/sleeping energy expenditure.
The Controversy Continues
Despite the evidence suggesting a link between CPAP and weight gain, some studies have shown different results. In 2019, a small study of 119 people found that more than half of participants experienced weight loss shortly after starting CPAP, while only 6% experienced weight gain. On the other hand, a 2021 meta-analysis on sleep apnea found that CPAP treatment resulted in significant weight gain, and that longer CPAP usage was linked to a higher weight increase.
Overall, the majority of large-scale, high-quality research indicates that CPAP use is more likely to cause weight gain, but this does not mean that weight loss is impossible during CPAP treatment.
Practical Considerations
Given the complex relationship between CPAP and weight, individuals undergoing CPAP therapy should consider the following:
- Do not rely on CPAP therapy alone for weight loss: People with OSA who are overweight should not expect CPAP therapy to be a sole solution for weight loss.
- Focus on lifestyle modifications: If you feel more alert and energized after CPAP therapy, it can be a great opportunity to increase your activity levels. When paired with a structured diet plan, CPAP may contribute to weight loss.
- Address underlying health issues: Weight gain after CPAP use appears to happen more commonly among people who already had existing issues with the regulation of blood sugar, such as those with diabetes.
- Consult with your doctor: Your doctor can help work through any concerns you have about CPAP and weight gain.
Additional Benefits of CPAP Therapy
While the effect of CPAP on weight remains a subject of debate, the therapy offers several other significant health benefits:
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- Reduced daytime sleepiness and increased alertness: Treating OSA with CPAP therapy has been found to reduce daytime sleepiness and increase alertness.
- Improved mood: Low oxygen levels associated with OSA may lead to brain changes that affect mood.
- Reduced risk of stroke: Using a CPAP machine for at least four hours per night reduces the risk of stroke among people who have OSA, by addressing fluctuations in blood pressure, low levels of oxygen in the blood, and high levels of carbon dioxide in the blood.
- Improved blood pressure: People with OSA face an increased risk of high blood pressure, and CPAP may help reduce blood pressure, especially in those who use a CPAP machine for at least four hours per night.
- Improved heart function: Research shows that treating sleep apnea with CPAP helps improve the heart dysfunction common in heart failure.
- Reduced headaches: OSA can cause a person to wake up with a morning headache, and CPAP therapy may provide relief.
- Improved insulin resistance: Studies show CPAP could improve complications in people living with diabetes.
CPAP Alternatives
Tirzepatide is a drug that’s been used for diabetes and for obesity and has been shown scientifically to improve obstructive sleep apnea. Antonio Culebras, MD, explains how the medication works, and how it might replace the CPAP machine that some people with sleep apnea wear when they sleep.
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