If there are two things we have to worry about a lot, they’re not getting enough sleep and eating too much saturated fat and simple sugars. And while these things seem to have nothing to do with one another—except, possibly, an abundance of birthday parties to attend—new research suggests that when combined, these habits can have major impacts on your health that you wouldn’t expect.In a study published in May 2014 in the journal PLOS ONE, gastroenterologists from Rush University Medial Center in Chicago found that mice whose sleep patterns were thrown off saw surprising changes in the makeup of their gut microbiome, but only when they were fed a high-saturated-fat, high-simple-sugar diet. Mice who also had their circadian rhythm messed with but ate little sugar and little saturated fat meals did not undergo intestinal changes.Yes, this study was done in mice, so the results have to be taken with a grain of rodent chow, but the implications of these findings are no small matter. The trillions of microorganisms that reside in your digestive tract and work together to help you break down food and absorb nutrients, and they also play an important role in gut health (for instance, helping to control irritable bowel syndrome and inflammatory bowel disease), and in your metabolic health as well. Gut flora have been shown to affect obesity and your mood.Sleep issues can throw of the delicate balance in the gut, thereby leading to major body-system disruptions and disease. The authors of this study note that you can throw off your circadian rhythms and start a chain reaction with something as simple as what they call “social jet lag,” or staying up later than usual with friends, then sleeping in more than usual on the weekends. And, no surprise, this kind of behavior often goes hand in hand with overeating on indulgent meals and dessert. Put the two together and—bang!—big trouble on the horizon.If chronic inflammatory disease isn’t exactly your idea of a thrilling party favor, think about this study when you’re pondering another piece of cake or staying out just a little bit longer and going to sleep just a little bit later.MORE: What’s Your Eating Style? Take the Quiz