If you’re stressing over whether to order those waffle fries, don’t. The damage has already been done.

Stress may be just as bad for our digestion as a fattening diet, according to a study conducted on mice by researchers at Brigham Young University.

In the paper, published in Nature’s Scientific Reports, researchers looked at the mice’s gut microbiota — aka the bacteria that live in digestive tracts that some research has linked to our metabolic health.

Scientists performed a stress test on the mice and found that the gut microbiome of female mice actually changed to resemble that of an obese mouse. Such a shift suggests that stress might impact metabolism just as much as diet, the researchers wrote.

Male rats didn’t have the same microbiome shift, but they did become more anxious and less physically active.

Though this study only looked at mice, recent research has pointed to stress as a culprit in obesity. For example, one study published in February in the journal Obesity found that levels of the stress hormone cortisol correlated to a larger waist circumference and higher body mass index.

It’s a modern-day inconvenience that actually helped us out back in the caveman days, Dr. Holly Lofton, director of the medical weight management program at NYU Langone Health, tells the Post.

When humans back then had a fight-or-flight response to stress — like escaping a predator — their “body’s glucose level rises to prepare to handle the situation,” she says.

Useful then, but not so great now. “When glucose increases, insulin rises . . . causing fat storage,” she says.

In general, the role of stress is becoming increasingly important in treating obesity, Lofton adds. She usually advises her obese patients to seek out ways to relax, like taking up meditation or something else that calms them, like painting.

“Stress management is a big part of weight management,” she says.