Originally Posted by John_V

While fluid retention is a very valid argument, I've only seen one post that addresses another valid point. If you are going to weigh yourself in the morning, do so after you have had a decent bowel movement. The intestinal tract can hold up to 5 pounds of poop and undigested food. This, along with any fluid retention can account for the increase in weight the next day, especially after having a heavy meal the night before.