Eggplant provides significant amounts of fiber and manganese, a mineral that acts as an antioxidant. As long as you don't load the eggplant down with fat by frying it with oil or adding fatty toppings such as cheese, it is also relatively low in calories. You can minimize the amount of oil absorbed by eggplant if you salt it before cooking, then rinse off the salt and drain the eggplant after about half an hour.
A cup of cubed raw eggplant has just 21 calories, and the same amount of boiled eggplant has 35 calories. More eggplant will fit into a cup when it has been cooked because it releases some of its water content during cooking. This accounts for the higher calories in a cup of boiled eggplant. Eggplant is usually coated with oil before baking or roasting, increasing the amount of calories it contains. The calories in the final dish vary, based on the amount of oil you use, but a cup of baked eggplant made with about 1 1/2 tablespoons of olive oil has 220 calories. Use just a spritz of olive oil cooking spray and you'll greatly reduce the calories in your baked eggplant.