WASHINGTON, Nov. 5 -- A lack of sleep may increase the risk of diabetes by reducing the body's sensitivity to blood-sugar-regulating insulin, a U.S. study said Thursday.

The study, published in the U.S. journal Current Biology, added to a growing body of information linking insufficient sleep to a range of ailments including obesity, metabolic syndrome, mood disorders, cognitive impairment and accidents.

"We found that when people get too little sleep it leaves them awake at a time when their body clock is telling them they should be asleep," lead author Kenneth Wright, professor at the University of Colorado.

"And when they eat something in the morning, it impairs their ability to regulate their blood sugar levels."

In the study, researchers looked at 16 healthy men and women in their early 20s.

Half of the test subjects initially slept for up to five hours a night for five days to simulate a regular work week. Then they slept for up to nine hours a night for five days.

The other half completed the sleep conditions in the opposite order.

Blood tests later showed that those who slept five hours a night had a reduced sensitivity to insulin, which in time could increase the risk of getting diabetes.

But when they slept nine hours a night, oral insulin sensitivity returned to normal. Still, it wasn't enough time to restore intravenous insulin sensitivity to baseline levels.

Wright said the problem could lay in our body clock.

"We have a clock in our brain which controls 24-hour patterns in our physiology and behavior. It also controls the release of the hormone melatonin which signals our body that it's night time," Wright said. "High melatonin levels at night tell us to sleep."

But if a person eats instead of sleeps during this time, the body has to release more insulin to keep blood sugar levels normal, he said.

"Our bodies can adapt initially but over the long term they may not be able to sustain it," Wright said.

The researchers said their next step is to test those at a higher risk of diabetes and see if improving the sleep of older people could improve their metabolic health.