How many people have gained weight using the breatheing machine blowing air while asleep?

Unknown: Using CPAP neither causes nor prevents weight gain. There is some evidence that it controlling appetite may be easier for patients using CPAP than for patients with untreated sleep apnea. I've been treating sleep apnea for over twenty years, and i've seen some patients lose weight, and many gain weight. The sad fact is that weight is more difficult to control as we age.