Hormones, Health & Weight Loss

From reading your post, I'm wondering how long a time horizon you were using to decide that (say) going over 1200 vs. eating 700 would cause weight loss? Days? Consistent weeks to months?

If we go from a very low calorie level to a more sensible one that permits good nutrition, it's common for the scale to jump immediately, and stay there for a bit. This isn't fat (re)gain, it's higher average digestive system contents in transit (food has weight, right? ), and higher water retention from issues related to the digestive process. Neither of those are fat, so not worth worrying about, although they can make the scale jump up in an alarming way (multiple pounds, even!).

On top of that, most pre- or peri-menopausal women are going to see water weight fluctuations of several pounds at different points in their menstrual cycles (and exactly when/how much differs individually). The hormonal impact is also not fat, just water, and not worth serious worry.

Realistically, a premenopausal woman needs to follow a consistent approach for long enough to compare weights at the same point in two different menstrual cycles, or more ideally three. A perimenopausal woman or just into menopause (as identified by cessation of periods) may have water weight fluctuations that are even more unpredictable. It kind of stinks, but that's how it is.

Most of the "calorie penalty" from aging (including menopause) is from a combination of two things: Reduced muscle mass, and reduced daily-life activity level (not just exercise, but what one's doing the rest of waking time). Happily, both of those are things we can almost totally control, via strength training and attention to movement in daily life. Intentional exercise is a bonus, mostly for health and fitness, since exercise calories are a small fraction of our day, and exercise needs to be fueled.

I'm 64, of course menopausal, and even hypothyroid. Eating 1200 (let alone 1000 or less) calories daily would put me in the hospital at a dangerously low weight in a matter of months, if I could stick to it (I wouldn't, and probably couldn't). I admit that I'm a good li'l ol' calorie burner for some mysterious reason, and some women really do need to eat 1200 to lose, but it's a rare non-bedridden woman who needs to eat much less to lose at a sensible rate (and odds are good that such a woman would be petite, not extremely overweight, fairly old, quite sedentary).

I'd suggest that you read this:

https://www.aworkoutroutine.com/1200-calorie-diet/

and this:

https://physiqonomics.com/the-weird-and-highly-annoying-world-of-scale-weight-and-fluctuations

If you haven't been tested for hypothyroidism, you might ask your doctor to run a full thyroid panel, especially if you're experiencing any of the other symptoms (fatigue, hair loss, feeling cold, body aches, etc.). Hypothyroidism has a relatively small calorie penalty inherently (5%-ish), but the fatigue can sap activity out of daily life and create a somewhat bigger effect. Hypo onset in later life isn't unusual. If fatigue is a symptom, while the doc is at it, consider requesting other nutritional tests (iron, B12, etc.) for issues that can be more likely to come home to roost as we get older.

With consistency and a manageble, practical plan and the patience to stick with it long enought to evaluate the true impact on body fat, you can do this. It's just my opinion, but I think menopause is really more of a post-hoc rationale, rather than a major cause, of weight loss struggle.

Best wishes!