You’re Eating Like a Caveman The diet: The Paleo Diet is exactly how it sounds: You eat only food that hunter-gatherers of the Paleolithic era would’ve eaten. Think: meat, fish, fruits, vegetables, and nuts—no dairy, refined sugars, or processed foods.Beauty benefits: Clear skin. Several studies have linked dairy to blemishes. One theory: Milk has hormones that may play a role in producing pore-clogging sebum. Researchers also believe that carbs can cause breakouts by increasing insulin, and ultimately inflammation in the skin.Not-so-pretty side effects: Again, you won’t see any negative effects if you don’t take it to the extreme. “Moderation is key,” says Dr. Zalka. You’re Committing to a Juice CleanseThe diet: There are as many juice cleanses as there are juices, but the concept is the same: Detox your body after—ahem—a holiday season filled with cookies, ham, and wine by only consuming fruits and vegetables in liquid form. Beauty benefits: Juices high in antioxidants reduce free radicals, making the skin look younger and less damaged.  Not-so-pretty side effects: “Short-term detoxes don’t shift long-term eating habits,” says Snyder. And highly restrictive diets can lead to binging, which isn’t just bad for your waistline; it can cause breakouts.You’re Saying Sayonara to CookingThe diet: Raw foodists believe that foods are most nutritious uncooked. That means no cooked tomato sauce, no soup, and usually, no meat. (Though some raw foodists follow an omnivorous diet.)Beauty benefits: “Vitamins and minerals are found in their greatest quantity when fruits and vegetables are consumed in their natural or ‘raw’ state,” says Dr. Zalka, Since studies show that vitamin C, which is common in produce, can improve the overall appearance of your skin, the diet can foster a brighter, younger-looking complexion. Still, some foods thrive under heat. Consider tomatoes, which release more lycopene—which has been shown to protect against skin cancer—when they’re cooked, as we said in 4 Popular Extreme Diets. The verdict? Adopt the diet if you want, but don’t do it for the skin fix alone. Not-so-pretty side effects: “Many ‘raw foodists’ eat a lot of dehydrated foods that dry out the skin and lead to under-eye circle and wrinkles,” says Snyder. Plus, it can make it harder for hair to grow in thick and full. If you’re brave enough to tackle this diet, staying hydrated is a must. MORE: 5 Anti-Frizz Hair Products That Work