I have long heard the idea that we must all have a certain number of calories a day (usually 1200 or more for women, 1500 or more for men) to prevent going into starvation mode. I am just not sure that is the same number for everyone.
I am, it turns out, a little person. (Who knew?)
When I go to The Daily Plate Calorie Calculator and type in my age, height, and weight, then select the setting to lose a standard 2 lbs. per week, the program tells me that I would need to eat 687 calories a day to achieve that.
When I go to FitWatch.com and use the standard Harris Benedict BMR (basal metabolic rate) equation to tell me how how many calories a day I will need to maintain my weight at goal, it generates a number of 1199 calories per day to maintain my body at rest.
That is usually how they calculate how many calories to give to someone in a coma.
My only offset option is to add activity and exercise, which I do. If I burn 400 more, I can eat 400 more, but the underlying physiological equation remains.
I think a great deal of what an individual needs will depend upon individual variables, like muscle mass and activity levels. Other things like thyroid function and so on are also personal variables. It seems that a given individual might actually use 10% to 30% more or fewer calories, depending on those factors.
A good rule of thumb for dieters is to start at the calorie level of your calculated BMR, adding in moderate exercise as able. After a while, you can see for yourself if that is an accurate level for you.