If you’ve been eating fast food for years, get real about your approach: You’re probably not going to stick to an organic, gluten-free, paleo overhaul for very long. "You want to change as little as possible to create calorie deficit," says Dr. Seltzer, who insists the best way to support sustainable weight loss is to incorporate small changes into existing habits. So instead of giving up your daily BLT bagels in favor of an egg-white wrap, try ordering your sandwich on a lighter English muffin. Or say you eat a snack bar every afternoon: Swap your 300-calorie bar for a 150-calorie alternative. "Your brain will feel the same way about it, so you won’t feel deprived," he says.

Sure, there's your one friend who swears by the Taco Cleanse. And that other friend who ate nothing but broccoli soup for a month and dropped 20 pounds, found the love of her life, and got promoted at work. But before you start blending 80 stalks of broccoli into a cup or crunching your way through a crate of tacos, check out which diets are backed by science. Because don't you want to try one that will do the trick for you?