What is salt and why does it make you fat? I touch upon this in my book, so here is the short version. Salt has been around for 4,000 or more years, being used in conserving meats and other foods. Chemically, table salt consists of two electrolytes: sodium and chloride, both of which are critical for your health. This is also the reason why one of your four types of gustatory receptors (taste buds) is dedicated only for detecting salt. Sodium regulates blood pressure and volume; if you consume too little or too much, the body will react with changes in blood pressure. In recent years, the typical Western diet filled with processed foods, which are loaded with salt. This leads to an over consumption of sodium, as well as calories. People very often eat too much sodium, which makes them reach for sugary, calorie-rich drinks. Salty foods are also easy to overeat, so calories can pile up. (Doritos with a soda, anyone?) The logical conclusion is that though not directly storing fat, salt can help you overeat.
The real problem with sodium
The dilemma, however, is not so much the amount of sodium consumed (assuming you are watching your intake) but the potassium/sodium balance. At cellular level, potassium is the counterpart of sodium: potassium gets pumped into the cell, and sodium goes out. This cycle repeats endlessly. The potassium/sodium ratio should be around one-to-two, but in reality it is closer to one-to-five since most people under-consume vegetables (potassium source) and overeat processed foods (loaded with salt).
So salt itself is not the enemy. As everything else, it needs to be consumed in moderation; 2,400 milligrams a day (half a tea spoon) would be a good average. To stay on the safe side, don't eat processed foods and be careful with your saltshaker. Also make sure to consume potatoes, beans, fish, and spinach as potassium sources.
If you plan a heavy workout the next day, add a little more salt to your dinner. The extra water can help to increase your strength during the workout. Sushi works wonders before squat day!