People who suffer a serious sleep disorder may also be at risk of liver problems, a study has suggested.
People with sleep apnoea have disrupted nights
Being overweight is linked to both conditions, but researchers from Paris' Hopitale Saint-Antoine say sleep apnoea may directly cause liver disease.
The Hepatology study said overweight people with the sleep disorder were more at risk than those without.
But a UK expert said just because there was a link did not mean sleep apnoea actually caused liver problems.
Thousands of people suffer from sleep apnoea, a condition in which they stop breathing temporarily during the night.
The problem can disrupt the quality of sleep, and lead to intense fatigue during the day.
People with sleep apnoea have been shown to have a higher chance of developing high blood pressure and therefore experiencing strokes or heart problems.
The French scientists looked at 163 non-drinkers who had fatty livers - where fat deposits build up in the organ, potentially leading to formation of fibrous tissue and then to cirrhosis or even liver cancer - to see how many of them had the sleep disorder.
Severe obstructive sleep apnoea (OSA) was seen in 27% of patients, while 52% had moderate OSA.
The researchers, led by Dr Lawrence Serfaty, found patients with severe OSA were more insulin-resistant and were more likely to have liver damage, compared to people of the same weight who did not have the sleep disorder.
John Stradling, professor of respiratory medicine at the Oxford Centre for Respiratory Medicine said there were many conditions which were inter-related and it was still unclear what was the initial cause
"Sleep apnoea goes with a lot of other things, such as high blood pressure, insulin resistance and metabolic syndrome [which increases heart disease and diabetes risk].
"It has been increasingly difficult to be sure that sleep apnoea is not just a result of all these things, which are themselves secondary to being overweight."
He added: "It's easy to find an association between two things, but it doesn't mean there is a causal link."
But he said it was possible that the oxygen surges which follow the repeated oxygen supply restrictions in the night could have a damaging effect on the liver.