Meal substitutes are drinks, powders, gels, shakes, or bars that offer a quick, convenient way to consume nutrients. Some meal substitutes are a source of protein, usually featuring soy protein or whey (derived from milk), or other forms of vegetable, milk, or egg protein. Other meal substitutes are primarily a source of carbohydrates. Meal substitutes contain sweeteners, flavorings, oils, fiber, vitamins and minerals, and other nutrients or herbs. They may also contain caffeine and other ingredients purported to boost energy, enhance performance, and promote weight loss. Used occasionally, these products can be a good meal substitute. However, they can also be high in sugar and calories, and may contain artificial flavors, colors, and preservatives. Check labels carefully, and choose meal replacements with a balance of protein, carbohydrates, and fat that’s appropriate for you. Make sure you get enough fiber and other nutrients by eating fresh fruits and vegetables, and use meal replacements only when you’re traveling, too busy to prepare food, or instead of fast food.