Water is very commonly the "elephant in the room" when it comes to food. We buy a pound of steak and wonder why it shrinks when we cook it, forgetting that it has the same sort of water content as we do. Butter and margarine typically contain only 16 to 18% water but low-fat spreads can be as high as 50% water. Celery has been described as "an expensive way to buy water". There are so few nutrients in calery that eating it is commonly reckoned to consume more calories than it contributes.