The governor of California, Arnold Scharzenegger, knows a lot about water retention. I have his 700+ page book, Encyclopedia of Modern Bodybuilding. He says that to be a champion of bodybuilding you have to have a minimum of bodyfat and water weight. Water weight does make you look fatter. He says that salt, saccharine, coffee and some medications cause you to retain water. He was taking a medication for an injury and it caused him to retain water so he did not compete because he does not like to lose.
When you retain water it means that your body is holding on to an excess of it or more than you need. The salt is stored under the skin and needs to absorb water so that it is not toxic. My website has a great deal of information of what salt does in the body. Bodyfat is burned off when you burn calories but it cannot be melted away with moisture or radiant heat. In fact the purpose for storing fat is not for moisture or radiant heat. It is the most efficient way to store energy to enable you to do things.
Exercise causes you to burn more calories. Walking burns as much calories as standing around talking, so it is good for circulation but not losing weight. Running is a high impact exercise that is hard on the joints. So instead do the Olympic event of powerwalking to lose weight. You walk as fast as you can keeping your arms up like when you are running. When people are in a sauna it does help them to lose weight. It is not due to sweating out water since you would gain that back as soon as you drink water. It is due to sweating out the excess salt that you are storing. Then you need to retain or store less water in your body so you lose water weight. The body is constantly getting rid of salt but a person consumes a great deal of it.
Biology teaches that plants create food out of minerals, air, sunlight and water and animals consume foods. Salt is not a food but is a mineral or rock. People get the sodium that they need out of foods with no salt added.
For example an avocado has 21 mg of sodium, a cup of red grapes has 3 mg, a cup of blueberries has 9 mg, a tomato has 10 mg, a cup of broccoli has 24 mg, a cup of cabbage has 14 mg and a half of cup of spinach has 22 mg of sodium. Note that all of these foods are known as being very healthy for you. The red grapes contain resveratrol. That is the nutrient that they say that makes red wine so healthy. So your kids can get this nutrient without drinking red wine.
The American Medical Association (AMA) is trying to get the FDA to take salt off the GRAS (generally recognized as safe) list and make it a restricted substance. Then they can control how much is put in foods including the food sold in restaurants. The AMA wants to reduce the salt in foods by 50% since too many Americans are dying from heart attacks and strokes.
A guy made a bet that he could consume 3 ounces of salt dissolved in water in an hour. He did that and then died. Since the salt needs to retain a lot of water so it is not toxic, you could say the person died of a lack of water or dehydration. This is why I call salt "anti-water." Sea salt is 98% salt so it is slightly better than salt. There is a Celtic Sea Salt that is 83% salt so it is better than regular or sea salt. When you cook foods it takes most of the flavor out of them causing a need for salt.