Strange as it sounds, the less water you drink, the more of it your body retains. If you are even slightly dehydrated your body will hang onto it's water supplies with a vengeance, possibly causing the number on the scale to inch upward. The solution is to drink plenty of water. A single teaspoon of salt contains over 2,000 mg of sodium. Generally, we should only eat between 1,000 and 3,000 mg of sodium a day, so it's easy to go overboard.
Sodium is a sneaky substance.
You would expect it to be most highly concentrated in salty chips, nuts, and crackers. However, a food doesn't have to taste salty to be loaded with sodium. The more highly processed a food is, the more likely it is to have a high sodium content. Be sure to read the labels on canned foods, boxed mixes, and frozen dinners. Women may also retain several pounds of water prior to menstruation.