By Mike Pomranz
Updated August 25, 2015
Credit: © Vintage Images / Alamy

For some reason, late night eating always feels guiltier. Maybe it’s because, despite what Taco Bell says, mom taught us there were only three meals, and even by some sort of romantic Spanish definition, dinner should have ended at least two hours ago. But new research claims there might be a biological component to our late night grubbing regret: Eating later may truly be less healthy.

“For years, we said a calorie is a calorie no matter when you consume it,” dietitian Joy Dubost, a spokeswoman for the Academy of Nutrition and Dietetics, told The Washington Post. “I don’t know if we can say that anymore, based on the emerging research. The timing of a meal may potentially have an impact.”

The Post cites two studies conducted at the University of Murcia in Spain. The first showed that people who ate their biggest meal before 3 p.m. lost more weight than those who ate their biggest meal after 3 p.m., despite all other factors—such as the amount eaten, sleep and exercise—being the same. The second found that eating lunch after 4:30 p.m. caused participants to burn fewer calories than when they ate lunch at 1 p.m.—once again, despite calories and activity levels remaining the same.

Other research points toward similar results. Kelly Allison of the University of Pennsylvania School of Medicine’s Center for Weight and Eating Disorders told the Post that studies show that the body is more likely to store calories as fat when people eat late at night. And Steven Shea, director of the Oregon Institute of Occupational Health Sciences at Oregon Health & Science University, says studies have shown that animals process food differently at different times of day.

Some scientists believe that our bodies are simply hardwired to process food and burn calories in different ways throughout the day thanks to our natural circadian rhythms. And though some studies have shown the potential benefits of certain types of late night snacks, in general, eating earlier tends to be the better way to maintain a healthy weight.