Anyone who's ever done shift work or suffered from jet lag has felt some of the havoc that a disrupted clock can cause. So how can you reset a disrupted biological clock? While the science behind biological clocks can get intricate, what's known about resetting a faltering clock is fairly simple.

There is actually more than one biological clock, with the master clock located in the brain and others positioned throughout the body. Normally they work together, but when they fall out of sync, problems occur.

As tasty as midnight snacks can be, they're biological time bombs.

Insufficient sleep is a major reason why clocks fall out of sync.

"We live in a society where sleep is not respected," says Eve Van Cauter, PhD, a professor of medicine at the University of Chicago. But she notes that sleep, circadian rhythms and metabolism are all intertwined.

Getting more sleep and shortening the part of the day when you eat appear to be the two simplest ways to help reset the clock and restore healthy metabolism. Many studies have shown that insufficient sleep wreaks havoc on people's metabolism. It’s been shown to lower the resting metabolic rate by enough to potentially lead to a 12.5-pound weight gain in a single year. And missed sleep makes people hungrier. But restoring normal sleep can help reverse these and other ill effects. That's one reason why sleep is sometimes called the world's easiest health tip.

It's also been known for a long time that the body handles food differently at night. One of the first signs of this was that some people who would test as diabetic at night would test normal in the morning. Even healthy people process sugar from nighttime meals more slowly than they do from morning meals.

It seems that tasty as midnight snacks can be, they're biological time bombs.

Simply by reducing their eating period from 14 to 10-12 hours, people lost an average of seven pounds.

Studies, mainly on mice, have shown that that periods of fasting, restricting eating to 8, 9 or 12 hours a day, have beneficial effects on weight, metabolism and circadian rhythms — even among those eating a high-fat diet. Hoping to extend these studies to people, researchers at the Salk Institute in La Jolla, California have created a phone app called myCircadianClock, which helps people track their eating, sleeping and activity patterns, as well as when they take medications or supplements. An ongoing study hopes to gather two weeks of data from about 10,000 people.

In a small pilot study researchers tested the app on eight overweight participants for 16 weeks. People in the study had been eating for a period of more than 14 hours each day. Simply by shortening their eating period to 10-12 hours, they lost an average of about seven pounds. They also reported sleeping better and snacking less. One of the app users called time-restricted eating “the best diet” because it didn't force him to give up any of his favorite foods. He’s still losing weight.

It's one more approach that people who have been trying to lose weight and haven't succeeded might consider.

The article, “Resetting the Circadian Clock Might Boost Metabolic Health,” with more information on our biological clocks, appears in JAMA, the Journal of the American Medical Association and is freely available.