Researchers at Pennsylvania State University found that when people drank 14 ounces of vegetable juice (which contains 88 calories) before lunch, they subsequently consumed 136 fewer calories during the meal. Because the beverage is thick and has a high water content, it helps take the edge of your hunger and enhance feelings of fullness, explains Barbara J. Rolls, PhD., professor of nutritional sciences at Pennsylvania State University and author of The Volumentrics Eating Plan.