Lose weight, gain weight, or stay the same. Which is it with CPAP?

Facts:  The more excess weight you carry, the higher your risk for sleep apnea.  Untreated sleep apnea is associated with an increased risk of weight gain due to multiple mechanisms.  Losing a significant amount of weight is associated with lowering sleep apnea severity, and sometimes it resolves.  

But what happens to your weight if your sleep apnea is treated?  Do you lose weight?  

This was the assumption for many years, and weight loss was often offered as an incentive to get your sleep apnea fixed.  The idea was that correcting daytime sleepiness would lead to more exercise since your energy levels presumably increase.  In addition, relieving sleep deprivation can reduce your food intake since the appetite hormones ghrelin and leptin fall back into balance.  Increased energy expenditure and reduced energy intake is supposed to be a formula for weight loss!

But the research on weight changes with CPAP treatment is all over the place.  Some people lose weight.  Some people have no change.  And some people gain weight with CPAP.  The amount of weight gained is usually up to 5 pounds or so (in a study population).  Interestingly, the increase in weight has been shown to be lean body mass as opposed to fat tissue.   

Note that the vast majority of research done on CPAP users identifies “compliance” with CPAP at 4 hours per night.  I interpret this as a low bar for intervention and wonder if more effect would be seen in those using CPAP consistently throughout the sleep period.  I don’t think there is anything particular about CPAP treatment itself causing weight gain, but I haven’t seen any meaningful studies of weight outcomes in people whose sleep apnea was treated with alternative therapies.

The status of your weight is dependent on multiple factors.  If it were as simple as “calories in, calories out” there would probably be a lot more weight loss success stories.   Anyone who has tried to lose weight by counting calories (including me) can probably relate.  

For those with very severe sleep apnea, there is a theory that struggling to breathe during sleep is a source of calorie burn- you’re effectively exercising as you sleep.  So getting your sleep apnea treated and sleeping more peacefully means you lose that exercise overnight.  Better for your health, but you might see the scale go up.  

In my experience, your chances of falling into one of these three groups (lose, gain, or stable weight) are about the same.  So I ask patients to be mindful of their weight as they start therapy.  If losing or maintaining your weight is your goal, you may need to adjust what you’re eating, when you’re eating, and how much you’re eating.  But do keep using your sleep apnea treatment- breathing is better.