There are no calories in salt - but if you are overweight/obese and you cut down on salt you will easily lose weight. If you cut down on calories you will not lose weight.
This is because obesity is caused by salt sensitivity/fluid retention and not by eating too many calories. This is why diets and calorie-counting do not work.
You do not need to eat less food to lose excess weight, because eating less food does not reduce fluid retention. Eating less salt reduces fluid retention and that is how it reduces obesity.
How to Lose weight!