If you don't seem to be losing weight or if your weight fluctuates in a very erratic and frustrating manner, it may well be your salt intake or just the imprecision of your scale.

I weigh myself everyday and track the standard nutrition label parameters every day - and fight the normal everyday weigh-in blues as a result. But this allows me to play with the data to see if anything useful can be observed.

Even after just three weeks, I have noticed a distinct correlation between sodium intake and apparent weight gain or loss. In the initial week, I lost 14 pounds. But my sodium intake was also in the basement at an average of 1350 mg per day reflecting a diet that contained virtually no prepared foods of any kind (which tend to have lots of salt added). In the second week, I fluctuated greatly with a week ending gain of 3 pounds. My average sodium intake during that week was around 3300 mg per day reflecting the addition of things like pepperoni to my diet. This week I was holding firm in the first part of the week and lost quite a bit in the second half. My sodium was higher in the first part of the week and lower in the second half with an average, so far, of about 3000 mg per day.

If you are going to weigh yourself everyday, you have to understand some basic facts about the rate at which your body's weight can change. A pound of fat represents about 3500 kcal of energy. You can't gain three pounds of fat in one day. Likewise, you can't lose three pounds of fat in one day. Anything much over half a pound in either direction is not fat - it is most likely water.

So how, might you ask, can your body store and dump so much water so quickly? It's the salt balance. The salinity of the human body is roughly the same as sea water which is about 35ppt (parts per thousand). This corresponds to a sodium concentration of roughly 10ppt. So if you dump an extra 10g of sodium into your body, your body has to hold onto an extra kilogram of water to maintain the sodium balance. This works out to about one pound for every 4000mg of sodium. I suspect that the process by which the body decides to retain or dump water due to sodium intake changes is in response to the sodium concentration at a certain point (within a certain organ) and so the weight swings are exacerbated by large swings in sodium intake.

If this is the cause of your fluctuations, don't worry too much. It is noise riding on top of your actual weight loss and while it can mask short term true weight changes it can't mask long term trends. However, I would suspect that it is better from a health standpoint to maintain a relatively constant sodium intake, but that it pure speculation on my part.

Also keep in mind that we are only talking about a change in the amount of water in your body by a fraction of a percent to perhaps a couple of percent in extreme fluctuations.

Finally, your scale is probably not precise to within a fraction of a percent, which you need it to be if you want to track changes of a pound in a person that weighs 200 pounds. Do this. Step on your scale and note the measurement. Now step off it and repeat a couple of time. Do you get the exact same measurement? Try it by stepping onto the scale very slowly and smoothly and try it by stepping on the scale quickly. Do you get the exact same measurement? Spring scales can easily vary by five pounds under such variations. To avoid this, you need to use a balance scale which will typically repeat their measurements within a half a pound or less.

wbahn, I really appreciate this very impressive and thoughtful post. I will pay more attention to my salt uptake because it makes perfect sense that salt swings=weight swings and that can't be good for a body.
Thanks very much,
nora

thanks wbahn for your words of wisdom, so glad U R a part of this forum. I personally never had a big problem with salt BUT I do know most people do. I just also read that if U increase your fiber intake substantually then U will most likely retain water too. The reason being that the fiber will expand inside of U holding the water. I personally would have more fiber and not worry about the small amount of water U will retain.