How bad are cheat days for you, really?

Some experts think cheat days are totally necessary to maintain your sanity. Others think they’re a recipe for disaster, leading you to overeat to the point that it actually hurts your weight loss and fitness goals.

The term "cheat" itself has negative connotations. The idea is that you're "good" if you eat clean, or "bad" if you cheat. This psychological barrier can be harder to overcome than the physical barrier of making small changes to your diet, which is why some people steer clear of cheat days completely.

So what’s the deal? Are cheat days harmless—or do they completely negate the hours of sweat you’ve poured into the gym?

What Is a Cheat Day, Anyway?

The idea of a “cheat day” has been around for decades. First, you eat “clean” for six days, meaning you stick to your diet. Your macros and calories are in check and anything that could be classified as “junk”—like fast food, dessert, and processed snacks—is off the table.

Then you let loose for the seventh day. This is where your Friday night beer-and-wings-showdown comes into play, because what's really the worst that could happen if you break the rules just once a week?

There's also a common misconception that cheat days can help boost your metabolism. The general concept: When you eat less, your metabolism slows down to “conserve” energy. When you eat more, it speeds up to digest and use that fuel. This, in theory, should allow you to stick to your strict diet for the remainder of your week.

The truth, though, isn’t quite that cut and dry.

How Do Cheat Days Affect Your Body?

The proverbial “cheat day” actually does nothing for your metabolism. Eating more to burn more isn’t quite how things work. Your metabolism does increase after you eat, but if you binge on 1,000 calories worth of pizza or brownies, your metabolism doesn’t ramp up to burn 1,500 calories to handle what you just consumed.

Plus, for some people, overeating can lead to other unhealthy habits. In a study published in the journal Obesity, researchers found that “obesity prone” individuals—based on personal and family weight history—who ate 1.4 times their estimated calorie needs were less likely to move throughout the day after overeating compared to those who were less prone to obesity. This lack of movement could put you at risk for weight gain, and even harm your health overall.

“I never recommend cheat days,” explains Jim White, R.D., owner of Jim White Fitness & Nutrition in Virginia Beach. “I have seen people indulge so much in one day that it ruins their weekly gains.”

That being said, cheat days can have an upside. Indulging occasionally has the potential to help some people stick to their diets, a study published in the Journal of Consumer Psychology suggests. The caveat: On their cheat day, the study participants still kept their portions in check, so they didn’t stray from their weekly calorie goals.

The Best Way to Approach Cheat Days

While the single-day binge can be helpful for some people, occasionally indulging in smaller portions of your favorite foods may be more sustainable for the long haul. That way, you can treat yourself a few times a week, rather than carving out an entire day to eat and feel like crap. Because let’s be real: while the idea of sitting down and slamming an entire pizza may sound appealing, the feeling of fullness after you chow down isn’t.

“Loosen up the reins a few times each week for some indulgent foods,” suggests White. “By allowing a couple smaller indulgences you give yourself a break from normal ‘dieting’ without sabotaging your results.”

To stay on track, only 10 to 20 percent of your calories should come from those treats. So if you're an average active guy who needs roughly 2,800 calories a day, 280 to 560 of those can be reserved for your “cheats” two to three times per week.

But what if those small treats are a slippery slope? If the idea of a small cookie, for example, puts you into a downward spiral of “I ate one, so I should enjoy the entire sleeve” then the weekly indulgence might be a better approach for you.

Either way, one meal or snack is never going to make or break your fat loss goals. You need to look at the big picture. Eating should be enjoyable and not so rigid that every morsel of food that crosses your lips is weighed, measured, and counted. If you’re considering an entire cheat day, it’s likely that the rest of your diet is a bit too restrictive in the first place.