Obesity is a major risk factor for obstructive sleep apnea, which is a serious sleep disorder that causes people to stop breathing for short periods repeatedly -- sometimes hundreds of times -- during the night.
In 2009, researchers from Sweden's Karolinska Institute showed that overweight and obese men who lost weight on a severely calorie restricted diet over nine weeks had big improvements in their sleep apnea symptoms.
In their newly published follow-up, the researchers report that the improvements were largely maintained over the next year, even though some patients regained much of the weight they had lost.
"Our earlier findings proved the principle that weight loss improves sleep apnea, but the criticism was that the patients would not be able to maintain the weight loss or these improvements," Karolinska Institute associate professor of clinical epidemiology Martin Neovius, PhD, tells WebMD.
The study included about 60 overweight and obese adult men with moderate to severe sleep apnea who lost an average of 40 pounds over nine weeks on a specially formulated, largely liquid diet totaling about 500 calories a day.
By the end of the diet period, a 58% improvement in sleep apnea symptoms was seen overall, with sleep apnea events declining by an average of 21 per hour.
Patients with the most severe sleep apnea saw the biggest improvements in symptoms and those who lost the most weight improved the most.
The yearlong maintenance phase of the study included monthly group therapy sessions and regular meetings with a nurse and dietitian.
Even though the men gained back, on average, about 14 pounds over the course of the year, collectively they still had a 47% improvement in sleep apnea symptoms; 10% of the patients no longer needed treatment with continuous positive airway pressure (CPAP) masks.
The study was published today in BMJ Online First.
Extreme Dieting Not Required
Medically supervised severe calorie restriction is used more in Europe than in the U.S., but Neovius says there is no reason to believe that weight loss achieved on a less extreme diet is any less effective for improving sleep apnea symptoms.