I wish I understood why we sometimes hold water and sometimes release it

I used to have very regular weight loss patterns. It followed my menstruation cycle pretty perfectly (if I were sticking to my eating plan). I would stay the same weight and then slightly gain for 14 days. Hold steady for 3 days, and then after ovulation, I would release all the weight for 9-10 days, stabilizing a day or two before my period. It was that predictable. My weight loss chart looked like stair steps going down.

But now I'm in peri-menopause. My cycles even if regular, are not the same quality. And I sometimes have anovulatory cycles. I'm 45. That's to be expected. So, my weight loss pattern has changed.

Since I started 3 weeks ago, my eating and movement (not much) have been consistent. The first 2 weeks I lost quite a bit every day - as is expected as my body depleted it's glycogen stores (glycogen holds water too). But, for the last several days the weight has been roughly the same. It's only a few days, I'm not worried or annoyed by it. I know it will come off as NO  WAY am I eating for maintenance, but WHY is it holding water is the mystery.

Yesterday, for instance, I weighed 1/10th of a pound less than today despite eating on plan yesterday. That is 1.6 ounces, or approximately 3 tablespoons of water/weight.  That's nothing? Right? So, no one should worry about it.

And actually, when you think about how little that is, it's amazing that we can not fluctuate more in weight day to day when we eat different foods, drink different amounts, have varying salts and minerals, and room temperatures can vary too (we tend to hold more water in hot weather than in cold weather). Somehow, miraculously, we tend to weigh about the same day to day despite all the things that can affect weight.

Getting a WHOOSH (say, losing 1 pound overnight) is the same as a tall glass of water. We think when we see it on the scale, "Wow! I lost a whole pound overnight!" Well, you didn't really lose it overnight, it's just the body finally released the water it was holding as you were dropping the fat/muscle.

So, why do we hold water? And more interestingly, why is some of it different for different people? I mentioned my menstrual cycle pattern. Most women don't have this pattern at all. Or, they have an opposite pattern, losing before ovulation and holding steady or gaining after it. I never gain weight during my period, many women do. THAT is super interesting as supposedly the same mechanisms are in play - same hormones being released, but how our bodies react to it are very individual. Akin to how some women get PMS with the hormone fluctuations and some women don't.

Basically, I'm fascinated with how the body works and I'm fully aware of how much we still don't know about how and why we work the way we do. And with such variations person to person, it's no wonder there is hardly anything that is one size fits all literally and figuratively.

Editing to add next day: and just like that, for absolutely NO REASON, I dropped 1.9 pounds overnight. Or, the equivalent of two of those tall glasses of water. Fascinating.