Damn it. I typed out a long response to your good question Mark and apparently it didn't get posted and it isn't saved as a draft.
Anyway, obviously we all vary due to our absorption, male vs female, body type, etc. so yes a smaller lady will not have the same requirements that guy sof our size would have. That being said, there is a certain number of calories needed in general to maintain weight for males and females. The generic average that is thrown out there often for a normie is 1,800 calories per day for women and 2, 400 for men.
Dianna who authored DS math will tell you that it was never intended to be used as hard fast math because as stated we all vary. It was just an average used to illustrate a general concept. So I am going to do a little math based on some common assumptions.
A gram of carbs has 4 calories
A gram of protein has 4 calories
A gram of fat has 9 calories
So for sake of illustration let's take a 100 gram protein, 100 gram Carbs and 100 gram of fat diet and see where calories shake out because at the end of day calories absorbed less calories expended determine weight loss, gain or maintaing.
100 g carbs at 4 cal/ram = 400 calories ingested (assume for this purpose a 100% absorption - isn't but we will go with it). 400 carb calories absorbed.
100 g protein at 4 cal/gram = 400 ingested (use 60% number for absorption) = 400 x .6 = 240 calories absorbed from protein
100 g fat at 9 Cal/G = 900 ingested (use 20% absorbed) = 900 x .2 = 180 calories absorbed.
This means a person ingested 1,700 calories and ended up absorbing 820 calories. Is it any wonder why we lose so much?
Now let't double everything and we get 3,400 ingested and 1,640 absorbed. That would maybe keep a female at her weight, but still isn't going to come close for most men.
Let's take my numbers: I eat around 250 grams of protein daily, around 250 (probably 50 more than I actually eat) I bet, and lets say 250 fat (I don't think I get anywhere near that & probably closer to 100 because I don't eat a lot fat) so:
Protein = 250 x 4 = 1,000 ingested and 600 absorbed using generic average DS math
Carbs = 250 x 4 = 1,000 ingested 1,000 absorbed
Fat = 250 x 9 = 1,000 calories ingested and 450 absorbed.
So for me I am around 2,050 calories a day absorbed withe the generic assumptions on absorption that we know we aren't supposed to take as gospel.
Obviously we all absorb a lot more than that average 60% number or we wouldn't survive. The question is how much and what is the break down.
This was just an exercise to explore a little. Yes we clearly all need different amounts of protein, carbs and fat and also in general ths exercise that I actually ran through the last week shows me that for me eating a significant amount of carbs is absolutely crucial and I also need lots of protein and fat.