More Americans are eating lunch at their desks or even forgoing it altogether. Is passing up a proper midday break bad for one’s health? Chris Cunningham, professor of Industrial-Organizational and Occupational Health Psychology at the University of Tennessee at Chattanooga, offers one view.

Brain Drain

The attention it takes people to focus at work drains them of psychological, social and material reserves, says Dr. Cunningham, leading to stress and lower productivity. “Taking a lunch break away from the desk lets people separate themselves from the source of that drain,” he says. “And that offers the opportunity to build back some of those resources in the middle of the day—rather than just at the end when work is over.”

There is no hard data on how much of a break the body needs to fully recover its resources, says Dr. Cunningham. He believes it’s person-specific; some might need 10 minutes, while others might need an hour.

Gravitate to Green

With so much research showing that parking in a chair all day puts a drag on productivity, mood and physical health, Dr. Cunningham suggests ditching the desk at least once at midday to do something energizing: “At least go for a walk down the hall.” If possible, he says, use the full break to switch focus to something uplifting—instead of, say, online shopping, reading email or running to the bank. “I wouldn’t call that a resource-replenishing moment,” he says.

Dr. Cunningham cites psychologist William James’s 19th-century concept of passive attention, which suggests that people can restock their inner resources by focusing on something that fascinates them and draws them in, seemingly without effort.

The easiest way to replenish, research shows: Interact with nature. “Just changing your environment relieves you of the need to decide what you want to attend to, and that in itself poses a sort of relief,” says Dr. Cunningham.

A Buddy Boost

Studies have also shown that connecting to colleagues socially throughout the day can be very energizing.

“If you’re a service rep or a call-center employee, I could understand why you wouldn’t want to take a social lunch,” says Dr. Cunningham, “but for some of us, it’s different enough from what we’ve been spending our day doing, and we get a lot out of it.”

He is a fan of going out with co-workers for lunch frequently—and not talking about work. “That is a resource-replenishing activity,” he says.

The only downside: “You can’t write that lunch off your taxes.”

Enjoy Eating

In a recent exploratory study, Dr. Cunningham asked medical residents to rate the degree to which they found each of their daily activities to be stressful, resource-straining and resource-replenishing. “Eating during work hours was the one activity that was rated only as replenishing, and tremendously valuable to them,” he says.

Nutritionists have long asserted that eating small amounts throughout the day helps maintain a level metabolism. And most people have experienced the sluggishness that follows a heavy midday meal.

“It’s certainly not advised to have a Thanksgiving feast for lunch,” says Dr. Cunningham. “Then again, you should give yourself a chance to be fascinated with the world around you—and enjoying your food can do that.”