Carbohydrates are one of three macronutrients, besides protein and fat, that you need in fairly large quantities to maintain your life and important body functions. They are revered for their ability to energize you quickly but also blamed for thickening waistlines in the rise of so-called low-carb diets. Nutritionists and public health officials still encourage you to get most of your calories from this nutrient, so it's important to learn to identify high-quality, healthy carbohydrates.