For a serving of eggnog (one cup), you will be consuming approximately 342 calories. Of those calories, 167 are from fat. Though eggnog has no sugar, it has a whopping 34 grams of carbs and 19 grams of fat. Furthermore, if you stock your fridge and go through a quart of eggnog, that is an incredible 1,368 calories, which is approximately one third of a pound! There is low fat eggnog available, which is a much healthier choice.