Can sleep apnea cause weight gain? The two-way link, explained

Sleep apnea and weight gain are linked in both directions. Extra weight is the biggest risk factor for obstructive sleep apnea, and there's good evidence that sleep apnea itself may make weight harder to manage, through hunger hormones, broken sleep and less daily movement. The research on the second half of that loop is smaller and mostly observational, so it's fair to say sleep apnea may contribute to weight gain rather than that it definitely causes it.

Does weight gain cause sleep apnea?

Weight gain is the best-established cause of worsening sleep apnea. AASM Sleep Education calls excess body weight the major risk factor and says you're much more likely to have sleep apnea if you're overweight (a BMI of 25 or more) or obese (a BMI of 30 or more). It also lists a large neck as a risk factor, because the extra soft tissue can block the airway during sleep.

The strongest long-term numbers come from the Wisconsin Sleep Cohort. Researchers tested 690 randomly selected working adults twice, four years apart. Compared with people whose weight stayed stable, a 10% weight gain predicted about a 32% increase in the apnea-hypopnea index (AHI), the number of breathing pauses and shallow breaths per hour. It also predicted a sixfold increase in the odds of developing moderate to severe sleep-disordered breathing.

The same study found the reverse too. A 10% weight loss predicted about a 26% drop in AHI. That's why losing weight is one of the main lifestyle treatments, and why our article on whether sleep apnea can go away spends so much time on it.

Weight isn't the whole story, though. Sleep Education notes that sleep apnea can occur in slim people too, and lists other risk factors including age, a deviated septum or nasal polyps, alcohol or sedating medication, and family history.

Can sleep apnea cause weight gain?

Sleep apnea may contribute to weight gain, and the clearest sign comes from what happens before people are diagnosed. In a 1999 study, researchers compared one-year weight histories in 53 people newly diagnosed with obstructive sleep apnea against 24 people matched for sex, age, BMI and body fat who had been confirmed by overnight testing not to have it.

The people with sleep apnea had gained an average of 7.4 kg in the year before diagnosis. The comparison group had lost 0.5 kg. The pattern held for both men and women. The authors concluded that people with sleep apnea may be susceptible to increasing obesity in the period before they're diagnosed.

A follow-up study in 2000 found a similar gap in 32 men. Those with untreated sleep apnea had gained 5.2 kg in the previous year, compared with 0.5 kg in similarly heavy men without it.

These are small studies, and they can't prove which came first. Weight gain could be pushing some people over the line into sleep apnea, and sleep apnea could be adding to the gain. Most likely, both are happening at once.

Why might sleep apnea cause weight gain?

Researchers have looked at a few explanations. None of them alone settles the question, but together they make the two-way link plausible.

Hunger hormones shift when sleep is short or broken

Two hormones do much of the work of regulating appetite. Ghrelin tends to increase hunger, and leptin tends to signal fullness. Sleep loss pushes both in the wrong direction.

In a small 2004 trial, 12 healthy young men spent two nights with restricted sleep and two nights with extended sleep, with their food and activity controlled. After short sleep, leptin was 18% lower, ghrelin was 28% higher, hunger rose 24% and appetite rose 23%. The biggest jump, 33 to 45%, was in appetite for calorie-dense, high-carbohydrate foods.

A larger study of 1,024 adults in the Wisconsin Sleep Cohort found the same pattern in everyday life. People who slept less had lower leptin and higher ghrelin, and among those sleeping under eight hours, BMI rose as sleep fell. The researchers estimated about 15% higher ghrelin with five hours of sleep compared with eight.

Neither of those studies looked at people with sleep apnea. They're relevant because sleep apnea breaks up sleep. Sleep Education explains that your body wakes up numerous times during the night, even if you're not aware of each awakening.

Ghrelin is higher in sleep apnea and falls with treatment

One study did look directly at people with sleep apnea. In a 2003 study of 30 men with severe sleep apnea, ghrelin was significantly higher than in people of similar BMI without it. After just two days of CPAP, ghrelin dropped in almost all of the men tested, to levels only slightly above the comparison group. Leptin fell after eight weeks, even though BMI hadn't changed. The authors concluded that these hormone levels aren't explained by obesity alone.

The body may stop responding to leptin

Leptin is often higher, not lower, in people with sleep apnea. In the 2000 study, men with untreated sleep apnea had higher leptin than equally heavy men without it, along with more weight gain. The authors suggested that sleep apnea may be associated with resistance to leptin's weight-reducing effects, meaning the signal is there but the body doesn't respond to it as well.

Less movement during the day

Sleep apnea is tiring. Sleep Education lists daytime sleepiness and fatigue among its common symptoms. A 2019 study in Sleep and Breathing used activity trackers to compare 35 overweight or obese people screened as likely to have sleep apnea with 24 people who weren't. The sleep apnea group took fewer steps and had fewer minutes of moderate activity.

Interestingly, the two groups didn't differ in BMI or reported sleepiness, so the authors said something other than obesity and sleepiness seemed to explain the gap. Some of the difference also shrank after adjusting for age. It's a small study, but it fits the picture of sleep apnea making an active day harder.

Will treating sleep apnea help you lose weight?

Treating sleep apnea doesn't usually cause weight loss on its own, and CPAP may even nudge weight up slightly. A 2015 meta-analysis in Thorax pooled 25 randomized trials with 3,181 people. Compared with control groups, CPAP was linked to a small but significant increase in both BMI and weight. The authors recommended that people with overweight or obesity who start CPAP also get help with weight reduction.

That result surprises a lot of people, given the hormone research above. Nobody knows for sure why it happens, and the meta-analysis didn't find a single factor that explained it. What it shows is that treatment and weight loss are separate jobs.

They do work well together. A 2014 trial in the New England Journal of Medicine randomly assigned 181 adults with obesity and moderate to severe sleep apnea to CPAP, a weight loss program, or both, for 24 weeks. The weight loss groups saw improvements in insulin resistance, triglycerides and an inflammation marker called CRP that weren't seen with CPAP alone. Blood pressure fell in all three groups. Among people who stuck closely to both treatments, the combination lowered blood pressure more than either one alone.

None of this is a reason to skip CPAP. Treatment protects your heart and helps with sleepiness, and our guide to sleep apnea and high blood pressure explains why that matters. It's a reason to add a weight plan alongside it if weight is part of the picture.

How do the main findings fit together?

Here's a summary of what each type of study tells us, and how much weight to put on it.

What can you do about it?

If you're gaining weight and also snoring loudly, waking up tired or being told you stop breathing at night, it's worth getting checked for sleep apnea. Our list of sleep apnea warning signs covers what to look for, and a home sleep apnea test is often the first step.

If you already have a diagnosis, the research points to a simple plan. Stay on the treatment your doctor recommends, and treat weight as its own goal with its own support. The Wisconsin data suggests even modest weight loss can lower your AHI, and the sleep apnea treatment options guide covers the medical routes, including newer weight loss medicine.

If you've been waking up tired for a long time, give treatment a fair chance to work before judging your energy levels. Better sleep may make exercise and food choices feel easier, even if it doesn't move the scale by itself.

This article is general information, not medical advice. Talk to your doctor about a plan that fits your health.

Read next

• Can sleep apnea go away?
• Sleep apnea treatment options
• Weight loss and snoring

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.