March 26, 2019 -- Obese adults with obstructive sleep apnea who follow a calorie-restricted diet can lose more weight if they also use a CPAP machine, according to a new study.

"CPAP can actually facilitate weight loss," says study leader Yuanjie Mao, MD, an endocrinology fellow at the University of Arkansas for Medical Sciences in Little Rock. He presented the findings Saturday in New Orleans at Endocrine 2019, the annual meeting of the Endocrine Society.

The findings presented at medical meetings are considered preliminary until peer-reviewed or published in a medical journal.

Sleep apnea is more common in obese people. It happens when people temporarily stop breathing, sometimes 30 times an hour or more, because their throat muscles relax too much and close the airway. The CPAP (continuous positive airway pressure) machine pumps pressurized air into their throat and lungs, keeping the throat muscles open.

Mao says the finding might lessen the resistance many patients have when their doctor suggests they use a CPAP. Patients often ask if they can try to lose weight first so they won't need the machine, he says. Based on the study findings, his new approach is to tell patients they may lose more weight if they start both at the same time.

But two doctors who reviewed the study aren't yet convinced that the findings apply across the board.

CPAP Study

The researchers looked at the records of 300 obese patients, average age 55, who were treated at the university weight loss clinic from January 2014 through August 2017. All took part in a 16-week program that included a very low-calorie diet (800 calories daily), an exercise program, and weekly counseling and behavioral therapy.

The researchers compared the weight loss in three groups:

  • 89 patients had no apnea symptoms so did not use CPAP
  • 164 had apnea symptoms but did not use CPAP
  • 47 had apnea symptoms and did use CPAP

Not all the patients had a sleep study, so Mao's team could not tell how severe the apnea was. Symptoms include loud snoring, daytime sleepiness, fatigue, or falling asleep during the day by accident.

After 16 weeks, ''the patients on CPAP lost 27 pounds, those with apnea who did not use CPAP lost 21, and those without symptoms lost 19 pounds [on average]," Mao says.  While the absolute weight loss was higher in the CPAP group, the percentage of weight loss was not significantly higher than the other two groups, Mao found.

Even so, Mao says that he believes, "If we start CPAP at the same time as a weight loss program, patients can expect to have more successful weight loss."

Second Opinions

The actual difference in weight loss among the three groups was ''not major," says Eric Kezirian, MD, a professor and vice chairman of head and neck surgery at Keck School of Medicine at the University of Southern California, who reviewed the findings.

"When I see this study, I am not totally convinced of the idea that CPAP is a key factor in enhancing the weight loss," he says, because there was such a range of body mass indexes (BMIs). The participants' BMIs ranged from more than 30, the start of obesity, to 49, morbidly obese.

While the researchers looked at the percentage of weight loss and the absolute weight loss, Kezirian says it would have been valuable to evaluate weight loss relative to a person's excess body weight, a common measure in weight loss studies. That measure takes into account height, gender, and other things.

In his experience, "CPAP alone without a diet can help people lose weight, regardless of dietary intervention, in selected patients." They sleep better, have more energy, and may be inclined to exercise more, he says.

Based on the study, he says he would not tell all patients on weight loss diets to count on CPAP to boost the loss.

Previous research has shown conflicting findings on how much a CPAP helps weight loss, says Matthew J. Freeby, MD, an endocrinologist at UCLA Medical Center in Santa Monica.

Freeby says a larger study is needed to verify these findings. "The group on CPAP may be very different than the other groups," he says. They may be more motivated both to use the CPAP and to diet, he says.

Show Sources

Endocrine 2019, annual meeting of the Endocrine Society, March 23-26, 2019, New Orleans.

Eric Kezirian, MD, professor and vice chairman, USC Caruso Department of Otolaryngology -- Head & Neck Surgery, Keck School of Medicine of USC, Los Angeles.

Matthew Freeby, MD, endocrinologist, UCLA Medical Center, Santa Monica; director, Gonda Diabetes Center, UCLA David Geffen School of Medicine.

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