The only downside to having vacations is that it takes a while for people to adjust to their time zones when they get back. People have to fight off jet lag as they try to ease in to their day-to-day schedules.

However, a new study has shown that people can get their bodies back in the groove fairly quick after a long vacation. Usually, doctors recommend avoiding alcohol and caffeine before sleeping to fight jet lag.

The study's author, Cristina Ruscitto, a researcher in the Department of Psychology at the University of Surrey, told the Huffington Post that the simplest way to lessen jet lag symptoms is just to eat breakfast, lunch and dinner on a normal schedule.

The idea, she explained, is "that you readjust by eating in line with local time ― not just sleeping on local time."

Ruscitto said that food keeps the circadian system — comprised of the central clock in the brain and the peripheral clocks in other organs such as the stomach, liver and lungs — in sync.

"Peripheral clocks respond to food and the central clock responds to light," she said. "Eating regularly provides information to the circadian system, telling the body to be active."

Ruscitto tested her hypothesis on 60 airplane crew members who had to fly to locations with a time change of at least four hours and a layover of at least 48 hours. The first group was told to eat meals on a "regular" schedule, while the second group was free to eat whenever they wanted. All of them were instructed to avoid napping before their flight or use sleeping pills after their flight.

Ruscitto discovered that there was no big differences in either group's alertness, but those who had regular meals were significantly less jet lagged compared to those who didn't.

"We found that making a meal plan to eat regularly (breakfast, lunch and dinner) before you travel did help reduce jet lag on days off [afterward]," she said. "The simple idea is to [keep] the circadian system in sync so that when you come back from a long-haul trip you readjust by eating in line with the local time ― not just [by] sleeping on local time."