"The number-one ingredient that I avoid in my diet is processed sugar. The reason: It speeds up the aging process by binding to and eventually weakening the collagen in your skin, which can lead to premature wrinkles and sagging. I eat lots of vegetables and fruits every day—and I steer clear of Twinkies at all costs!"—Ava Shamban, MD, dermatologist and owner of the Laser Institute for Dermatology and Skin care, Santa Monica, Calif.