I limit my sodium intake when I'm cutting because sodium makes me retain a lot of fluid. This, in itself, is not a hinderance to fatloss. However it makes gauging my progress difficult if the scales are changing all the time. One way around this is to measure your sodium intake just like you macronutrient intake. In other words, work your diet so you know you're getting X grams of sodium per day (no more, no less). Then you know that weight fluctuations are not caused by sodium balance. I also limit my sodium because I am prone to essential hypertension, and my father and grandfather have died from heart failure, but this is irrelevant to you if this is not an issue. The best way to tell if your sodium sensitive is to follow a low salt cutting diet for a few weeks (and make sure you're losing weight). Then have your weight and BP measured. The next week add salt into your diet and have your weight and BP remeasured. If your weight or BP has increased (and nothing else has changed in your diet/training except the sodium), then there's a good chance you're sensitive. It's not really anything to worry about except that it can affect the weight readings.
This is all pretty off the cuff. Hormonal changes due to stress, menstral stage, heat, humidity etc...can also affect water balance. The most important thing is to drink PLENTY of water, no matter what you eat.
This is all pretty off the cuff. Hormonal changes due to stress, menstral stage, heat, humidity etc...can also affect water balance. The most important thing is to drink PLENTY of water, no matter what you eat.