My personal experience is that folks generally have two caloric ranges at which they lose weight, one extremely restricted and generally slowing the metabolism - this is the one most folks know really well - "not losing weight? drop your calories!" The other is generally 500 or so calories (up to 1500 calories for some folks) above the restricted one. It goes along with the theory of eat more, boost your metabolism, weigh less.

The simple fact is, if you are losing at the current program, what exactly are you questioning? The why? The science? To me, deficits should be looked at on a 7-14 day average. One day is not the end of anything. I personally don't even really track calories. It is such a flawed science. I am relearning how to eat to actual hunger.

I also find that women, since we have that lovely monthly hormone cycle, tend to lose in "whooshes" anyway. We might not lose all month, then the week after "Aunt Flo," we have a whoosh that represents the monthly balance of our actions. They say that the scale, aside from obvious water retention, reflects what you did 2 weeks ago, not 2 days ago, etc.

Also, I will go against the current popular notion that IIFYM works - and it does, but only if you set up your macros for your specific health issues. Basic "standard" macros do nor work for everyone, and particularly they generally don't work for anyone with a damaged metabolism or hormonal issues - i.e., that is generally nearly every single person with either PCOS or IR, much less both! What I mean is that I can eat 500-1000 calories MORE on a low carb plan than I can on a high carb plan and still lose weight. So if I am eating 50% of my food from carbs, I have to restrict my calories in order to lose weight. But if I am eating 5-10% of my food as carbs, I generally don't have to restrict myself beyond common reason on the calorie side. I have a damaged metabolism. I have PCOS, suffer IR, have hypothyroidism, have low stomach acid, had my gallbladder removed, and probably a dozen other things I'm forgetting. Because of that, I have to eat a specific way to support my health.

And frankly, when it comes down to the wire, I'd rather lose fat and inches than pounds on the scale any day...which is what is currently happening for me, due to a ridiculous number of factors...

Oh, and when I say that calories are a flawed science, I mean that nutritional labeling can have up to 20% errors across the board permissible. Food manufacturers often do this on purpose. They manipulate portion size to huge or tiny sizes to improve the appearance of a serving's numbers - this is why most cheese says 0 carbs, even though it is often 1 carb for 2 oz, but they can round down if they say the portion is 1 oz, etc. Same with heavy cream, and all manner of foods. Add to that the notion that the calorie itself is created in a lab as far as creating values, but this doesn't take into account dozens of other factors in the body, and without hydrostatic or specific metabolic testing, we really don't know our true caloric needs/burns/etc. So it's all an estimate. So just choose a method, be consistent, and if you are losing weight, keep it up...

So, I kind of didn't understand 100% what you were asking - and I kind of hit upon a bunch of different things here... Let me know if I answered what you were looking for, etc.

Ok-- first of all, ditto to @KnitOrMiss 's mention of female hormone cycles. I have 2/4 weeks a month where my weight plateau's or goes up due to hormones & then I get the water "whoosh's"...It is totally due to ovulation week & menstruation (when I'm not preggers, like now. lol). I try to look at overall monthly trends when assessing how I'm doing, even though I keep up the daily weighing habit (due to scientific curiosity).

That being said, I do have a threshold of calories that if I eat below that, I lose weight slower. For me that is a floating range of around 1600-1700 calories. If I eat closer to the 1500 mark, no matter how low carb & how much I'm lifting/working out...the scale doesn't budge...for months. I also found that I did the best when losing weight, if I kindof flexed my calorie intake every day. Some days down 150kcal, some days up 300kcal, etc. It seemed like if I got overly repetitive in how much I ate & WHAT I ate (i.e. same meals multiple days in a row), my metabolism would just give me a big "screw you" & I'd stop losing.

Just other things to keep in mind.

I'm also a mathematics/science-driven individual... but to a certain degree, with PCOS you have to let go of that. Our bodies aren't "normal"...they are not going to follow "normal" logic with attempts at weight loss. For PCOS it's not purely calories-in/calories-out, but more a breakdown of what is consumed, when it's consumed, etc.

Hang in there .