You've heard the expression "You are what you eat," and to a large extent, that's actually true. All the grooming products in the world won't matter if the stuff you put inside your body is crap. "The skin is not separate from the rest of the body," says Valerie Treloar, M.D., founder of Integrative Dermatology in Newton, MA, and co-author of The Clear Skin Diet. "Your skin cannot be healthy if your body is not healthy — no matter how much stuff you slather on. For healthy skin, you need good dietary nutrition." The foods you should focus on are ones rich in vitamins, protein, and essential fatty acids. "Deficiencies in any of these things will cause skin abnormalities that have a huge impact on skin quality," Treloar says. Note: That doesn't mean a lunchtime binge on grilled salmon and a spinach salad is going to gift you a photo-worthy face by tomorrow. "With acne and rashes, you might see improvement in your skin within a few weeks of eating the right foods," says Jessica Wu, M.D., a Los Angeles dermatologist and author of Feed Your Face. "When it comes to anti-aging issues, it can take months to see the results. Eating for good skin is definitely a lifestyle change, not a one-time 'diet,' but look at it this way: You wouldn't think twice about putting premium fuel in your sports car, so why not treat your body the same?"