Like other legumes, lentils are low in fat and high in protein and fiber, but they have the added advantage of cooking quickly. Lentils have a mild, often earthy flavor, and they're best if cooked with assertive flavorings. Brown Lentils tend to get mushy if overcooked. If you want them to be firm, add oil to the cooking water and cook the lentils just a short while, say 15 minutes. Best used in soups.