You want to be at the top of your game when you’re traveling on business, but crossing time zones can take a toll on even the most experienced travelers.

“Know the time zone that you’re going into, and a few days before, adapt to that time zone.”

- Maggy Dunphy, executive director of spa and wellness for Destination Hotels

Business travelers who have crossed time zones experience diminished mental capacity and communication skills as well as a decrease in their ability to concentrate and engage with others. They also have a greater chance of becoming ill, according to an AirPlus International study done in partnership with Business Travel Market, a market research firm.

The study corroborated research conducted by National Highway Traffic Safety Administrator Mark Rosekind when he was director of NASA’s fatigue countermeasures program. Rosekind found the average executive’s productivity and performance drop up to 20 percent while traveling, mostly because of insufficient sleep.

So how do seasoned American travelers combat sluggishness when they cross time zones to meet with clients in Brussels or Hong Kong, or to make a presentation in Paris?

The best way to fight back is to adjust your behavior to the time in your destination, stay organized, set two alarms and get a wake-up call, if necessary, to make sure you get to your appointments.

Experts say it typically takes one day to recover for each time zone you cross –  as much as two weeks, depending on how far you’re traveling – and preparation is the best antidote. Some say it’s tougher going east than west, but others feel the impact no matter what their direction.

Experienced travelers know the best ways to combat jet lag include hydration, exercise before, during and after the flight, and eating the right foods – but not too much, since you want to get some sleep and wake up refreshed at your destination.

Here are some other best practices of frequent business travelers:

Adjust your body clock:  Several days before you travel, modify your sleep schedule slightly earlier (if traveling east) or later (if traveling west). “Start to adjust your sleep pattern several days before you travel so it’s not so much of a shock when you get there,” said Maggy Dunphy, executive director of spa and wellness for Destination Hotels. “Know the time zone that you’re going into, and a few days before, adapt to that time zone.” Roger Boyd, founder of 1Above, an Auckland, New Zealand-based company that promotes health for travelers, adds that you should switch your watch to the time zone you’re traveling to as soon as you get on the plane.

Control your environment:  Use earplugs or a noise-canceling headset and an eye mask to shut out sound and light when preparing to sleep. Bring a neck pillow (and a blanket) with you to stay warm. “Everything that helps induce relaxation, not just sleep, helps,” said Josie Feria, director of spa operations at Lapis, The Spa at Fontainebleau, Miami Beach. From the whirring of the engines to the low humidity in the cabin, “you are aware of everything going on around you,” she said.

Hydrate: Drink enough fluids in flight. Some experts advise eight ounces per hour. “I try to stay hydrated before and during my flight,” said Bob Jacobs, vice president of brand management for Westin Hotels.

Exercise: “Walk around a lot during the flight,” said Jacobs, a marathon runner who wears compression socks when flying to ward off deep venous thrombosis (DVT). Then get some exercise when you land. “I run when I get there,” he said. If the airplane cabin is too small to walk in, Feria suggests rotating your ankles clockwise and counterclockwise and rolling your shoulders while stuck in your seat.

Eat right: Skip high-salt foods and rich meals. Choose vegetables, salads and fruit over the complimentary salty snacks some airlines offer. Boyd suggests protein-rich meals for breakfast and lunch and a carbohydrate-rich meal at the end of the day to help you sleep. Jacobs recommends a banana smoothie made with plain yogurt and honey to induce sleepiness. If you want to indulge in a big meal, wait until the last night, when you no longer have to be at peak performance the next morning.

Avoid caffeine and alcohol: As much as you may love them, they can contribute to dehydration.

Aim for light exposure: Upon arrival, if it’s morning, head outside for a walk or run to stimulate your circulation and your mind.

Calm your mind and body:  Spa treatments like a Swedish massage or hydrotherapy can help your body adjust. “Soak in your room tub with Epsom salt added to the water,” Feria said. “It will reduce inflammation.”

Consult your doctor: If you are tempted to try over-the-counter remedies or to mix prescription drugs while traveling, check with your personal physician before you fly.