While mixing two of your favorite things may sound harmless, adding fatty foods and booze to the mix heavily taxes your body’s performance. “You’re just setting yourself up for gastrointestinal distress,” says Liz Applegate, PhD, director of sports nutrition at the University of California in Davis and author of Eat Smart, Play Hard. “You can get gas, bloating, and even diarrhea from simply taking on board too many carbohydrates, especially if you haven’t trained with them.” How many carbs do these races come with? Novelty races include everything from cupcake runs, to wine marathons, hot chocolate 15Ks, and even a Dallas race where you’re served both beer and doughnuts at pit stops.  Sure, you need fuel on a long run, but pastries and beer are a little different than gels and sports drinks. “Cupcakes and doughnuts are more than just sugar,” Dr. Applegate says. “They have fat in them, which will sit in your stomach for a longer period of time and could lead to a side stitch, nausea, and vomiting.”  And while beer does have some potassium and carbohydrates, its high alcohol content has some serious downsides. It messes with your coordination, busies your liver with alcohol metabolism instead of muscle healing, and tells your central nervous system to relax, meaning you’ll have to fight to the finish.  If you’re still itching to take on the challenge, however, take it easy and sign up for a shorter race than you normally would (say, a 10K instead of a half-marathon). “If it’s not making you puke, it’s not a huge problem,” says Jordan Metzl, MD, a sports medicine physician at New York City’s Hospital for Special Surgery and author of The Exercise Cure. “The problem is when you try to do a fun event like this at intensity.”  Dialing down the competition, in turn, can make it rewarding and, dare we say healthy, in a different sense. “We know that social ties are a great predictor of long-term adherence to physical activity,” says Jessica Matthews, an assistant professor of exercise science at Miramar College. “[In this case] it’s really more social; it’s about making new friends.”  More from Prevention: 18 New Running Workouts