Even the fittest guys will admit it: We all love to dig into a fat, greasy burger or a few glistening slices of greaseball pizza every now and then. Taking a break from a strict diet when trying to get shredded for catching more glances at the beach is an essential part of the process—you need that infusion of crazy calories to boost energy and your metabolism, plus free your psyche from the constant tedium of chicken and rice and veggies.

But going too crazy with high-fat meals on your cheat days could harm your liver and even set it up for higher risk of future fatty liver disease, says a recent study from the Diabetes Center at Heinrich Heine University in Dusseldorf, Germany.

For the small study, scientists gave 14 healthy young men 1.18 grams of palm oil per kg of bodyweight (or a placebo) on two occasions, separated by 8 weeks, similar to the amount of saturated fat you would get with an order of a cheeseburger and large serving of fries.

The results were startling, with the immediate effects mimicking the types of changes you see that can lead to fatty liver disease and non-alcoholic cirrhosis, said the study authors. The large amount of saturated fat eaten also made the liver bump up production of glucose by 70%, which can lead to high blood sugar levels and insulin sensitivity, a sign of pre-diabetes. Healthy people may be able to limit the bad effects of fat bombs on the liver, but continuous consumption could be disastrous for overweight and inactive folks, the authors noted.

The silver lining, the authors said, was that by simply switching to healthy unsaturated fats like olive oil or canola oil, and eating foods full of omega-3s like fish and monounsaturated fats like those found in nuts, you can quickly drop liver fat levels in a few days. To learn more about what kinds of fats you should be including in your diet, along with what foods to find them in, check out the 7 best healthy fats to eat.