A week in the wilderness, with nights lit only by the glowing embers of a camp fire, may be just the thing for incurable night owls.
Camping out for a few days and nights can re-set the biological clocks of people who have trouble sleeping and getting up in time for work, research has shown.
It seems that given the chance, our bodies naturally adjust to the light-dark cycle of the rising and setting sun.
"By increasing our exposure to sunlight and reducing our exposure to electrical lighting at night, we can turn our internal clock and sleep times back and likely make it easier to awaken and be alert in the morning," said US sleep expert Dr Kenneth Wright, from the University of Colorado at Boulder.
Dr Wright's team recruited eight volunteers who habitually stayed up until after midnight and wake around 8 am.
Measurements of the sleep regulating hormone melatonin showed that their busy lives had delayed their internal, or circadian clocks, by around two hours.
As an experimental therapy, the group was taken out summer camping in Colorado's great outdoors.
Though camp fires were allowed, all forms of artificial light - including torches - were banned, as were distracting mobile phones.
Participants were told they could sleep according to whatever schedule they chose. After a week of being exposed to nothing but natural lighting, their biological clocks were re-set roughly two hours back.
Even though the total amount of time they spent asleep stayed the same, the volunteers awoke at daybreak and were ready for bed when the sun went down.
It was more than just habit. Tests showed changes in fluctuating melatonin levels that contributed to feeling more refreshed and alert in the morning.
Under "modern world" electrically lit conditions, melatonin only reduces to daytime levels some two hours after waking, which explains why it is so hard to rise and shine when the alarm goes off.
But after exposure to natural light-dark cycles, the hormone dips during the last hour of sleep, according to the scientists writing in the journal Current Biology. As a result, the brain is able to rouse itself earlier, and waking up is not accompanied by grogginess.
If heading for the woods is too impractical, simply getting more sun might help, the scientists believe.
"Our findings suggest that people can have earlier bed and wake times, more conducive to their school and work schedules, if they were to increase their exposure to sunlight during the day and decrease their exposure to electrical lighting at night," said Dr Wright.
The research also showed that individual differences in sleep timing were reduced by exposure to natural light conditions.
"Internal biological time under natural light-dark conditions tightly synchronises to environmental time, and in this regard humans are comparable to other animals," the scientists wrote.Suggest a correction