Feeling Discouraged

I easily retain 3 lbs of water after eating lots of sodium, and it takes 2 or 3 days for it to settle back down.

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To add to comments above: I don't know your age, but among pre-menopausal women, it's absolutely common to gain several pounds of water weight at some point during your menstrual cycle. Reportedly, it can happen any time between ovulation & the end of menses.

Unlike some above, I prefer to weigh myself daily. For me, it helped me understand the daily fluctuations, what causes them, and how rapidly they reverse. Nowadays, fluctuations don't stress me at all, and I can often predict when they'll occur. But this is not for everyone: One does need to be able to avoid freaking out about the little changes until the patterns clarify in one's mind. If it's super stressful for you, then weighing less often may help.

There are even weight trend apps you can use to record your weight, then the app makes a statistical estimate of your weight loss direction, kind of smoothing out the daily bumps so you can better see the trend. Happy Scale (for iOS), Libra (for Android), and Trendweight are just a few examples.

Personally, I've seen a change of as much as 3-5 pounds on the scale from one day to the next, without having eaten anything even remotely close to the 10,500-17,500 calories above maintenance calories that it would take to gain that much fat.

In your case, it's certainly water weight, perhaps from the sodium, perhaps from your cycle - and there are other potential causes of water weight, too. If you know you haven't eaten 3500 calories above maintenance, you haven't gained a pound, let alone 3.

Take a deep breath, stay on your healthy course, and the water weight will drop off, probably in 2-3 days (if sodium), or a week or so (if monthly cycle). You're doing fine.