Your diet could be to blame.

A new study from the University of South Carolina, published recently in the journal Nutrients, found that those who ate more inflammatory foods slept worse than those who ate less of them.

Dr. Michael Wirth—one of the study’s lead authors, and an assistant professor of epidemiology and biostatistics at the university’s Arnold School of Public Health—tells Fortune he’s looked at the role of inflammatory diets in a number of different groups: police officers, pregnant women, and men in general.

All such studies came to the same conclusion: When people move toward a more anti-inflammatory diet, they sleep better.

They don’t necessarily sleep longer, Wirth cautions. But they spend more time in bed asleep, without waking up. And they get more quality sleep. “It improves their sleep efficiency,” he notes.

Why? High levels of inflammatory markers like interleukin 6 and tumor necrosis factor inhibit the natural rhythm of the sleep-wake cycle, Wirth says. If someone’s diet frequently contains inflammatory foods, “you lose that natural rhythm.”

How to move toward an anti-inflammatory diet

His advice to those who want to improve their sleep via diet: Don’t start drastic.

“One thing I try not to do is say, ‘Hey, take your diet and completely change everything about it,’” he says, adding that Americans, in particular, don’t respond well to such demands on their freedom.

His suggestion instead: Start by adding just a couple of anti-inflammatory foods to your diet regularly.

Some anti-inflammatory food options:

• Green, leafy veggies like spinach and kale
• Fatty fish like salmon and tuna
• Brightly colored fruits like strawberries, cherries, oranges, and blueberries
• Nuts like walnuts and almonds
• Hot, colorful peppers like jalapenos and habaneros

Even smaller changes can make a difference, like adding spices, herbs, onions, and/or garlic to the dishes you had already planned to make. Spices and herbs in particular are ““some of the most anti-inflammatory foods on this planet,” Wirth says—an effect opposite of what you might expect, given their zest and heat.

If you find yourself sleeping better and are looking to take things a step further, cut down on animal protein and foods “that come in a box,” Wirth recommends.

He references the notion of “shopping on the outside of the store.” If you stick to the parameters, you’ll encounter what’s fresh—fruits, veggies, protein, dairy, and the like—and avoid processed foods chock full of unhealthy preservatives and additives.

If that seems too tall of an order, focus on snacks first, Wirth suggests, as they’re typically the main source of processed foods in a diet.

Inflammatory snacks to avoid include:

• Chips
• Cookies
• Crackers
• Pastries
• Cereal
• Snack cakes
• Sodas and sweetened drinks

Other good foods to limit due to their inflammatory status: fried foods like fried chicken, and those laden with oil, like many pizzas. 

Eliminating even one or two inflammatory foods from your diet will put your body on a path toward healing, Wirth advises. And you can expect to be paid in benefits both short- and long-term.

“After two, three, four nights of really good sleep, you’re going to start to see changes in alertness during the day, the ability to think on your feet, physically not being as tired,” he says.

Further out, expect a reduction in risk for obesity, heart disease, cancer, and other maladies.

When inflammation disrupts the body’s natural circadian rhythm, more than just sleep is affected, Wirth cautions. So is “everything from your body’s ability to fight off infection and digest your food, to prevent insulin resistance.”

The good news: Small, positive diet choices can begin moving the needle back—quickly.

Adds Wirth: “You’re going to feel better, be able to think better, do things physically better.”