Class 3 obesity—defined as a BMI higher than 40 kg/m2—is associated with an increased incidence of hypertension, T2D, heart disease, and obstructive sleep apnea (OSA). “There is an increasing number of people with class 3 obesity who present for help with weight loss,” says Milan K. Piya, FRACP, PhD, FRACP. “In addition to complications from obesity-related comorbidities, these people have higher mortality and morbidity rates. These risks can be reduced with significant weight loss, but significant sustained weight loss in the absence of bariatric surgery is difficult to achieve in the most cases.”

Continuous positive airway pressure (CPAP) is a first-line treatment for moderate-to-severe OSA, but compliance with CPAP is often suboptimal. “Many patients who present for help with weight loss often feel that their OSA makes them less likely to lose weight,” Dr. Piya says. “In addition, many patients with OSA are unable to tolerate or afford CPAP therapy, which can also impact patient perceptions on their ability to lose weight.”

Understanding of Impact of OSA & CPAP on Weight

While the association between obesity and OSA are well established, there is conflicting evidence on whether the presence of OSA makes weight loss easier or more difficult for patients, according to Dr. Piya. “There is even less data on people with class 3 obesity who attempt weight loss and have OSA, and how treatment with CPAP affects outcomes,” he adds.

For a study published in BMC Endocrine Disorders, Dr. Piya and colleagues compared weight loss over 12 months between patients with class 3 obesity and with and without OSA within the context of an intensive multidisciplinary weight management program. Investigators also compared weight loss between those who used CPAP for 4 or more hours per night and those who did not in patients with class 3 obesity and OSA. Additionally, they assessed if baseline sleepiness was associated with weight loss at 12 months. “Our goal was to understand the impact of OSA and CPAP on weight outcomes in people with class 3 obesity attending a multidisciplinary weight management program,” says Dr. Piya.

Significant Weight Loss Seen in Patients With & Without OSA

Results from the study showed that the presence of OSA at baseline or the use of CPAP did not appear to affect weight or glycemic outcomes at 12 months in people with class 3 obesity who attended a medical weight management program (Figure). “The key finding from our study was that if patients are part of a weight management program, their chances of losing weight at 12 months are similar, regardless of whether they have OSA or use CPAP regularly,” Dr. Piya says. “As expected, OSA rates were high, with about two-thirds of patients being diagnosed with OSA at baseline. Weight loss at 12 months was 6.5% overall, with about 60% of patients losing 5% of their initial body weight in that time.”

In addition, the study authors reported that for all three groups, patients reported being less sleepy compared to baseline at 12 months based on an Epworth Sleepiness Scale. In patients in T2D, the researchers observed a significant reduction in A1C levels from baseline to 12 months, but again, there were no significant differences between groups.

Focus on Lifestyle Changes & Medical Weight Management

“The findings from our study suggest that while diagnosing and managing OSA is still important for overall health, it may not affect weight loss outcomes,” says Dr. Piya. “Therefore, when managing patients with OSA and obesity who are attempting to lose weight, a focus on lifestyle changes and medical weight management is important. Weight loss will improve overall health and sleepiness regardless of CPAP. Importantly, a diagnosis of OSA should not discourage people from attending weight management programs or attempting weight loss.”

The study team noted that additional research is warranted to help corroborate their findings. “A randomized controlled trial across multiple centers and with longer follow up would be needed to study the effect of OSA and CPAP therapy on weight loss,” Dr. Piya says. “Furthermore, larger numbers of participants would allow us to classify patients with mild, moderate, and severe OSA to see if disease severity affects weight loss outcomes.”