A certain well-known book advocates about 1200 calories per day as an appropriate amount for a woman, and about 1500 for men. I consider this advice INSANE. No wonder people get eating disorders, trying to follow advice like this, INEVITABLY failing (because it's grossly inadequate) and then blaming themselves for the failure.
In the infamous "starvation experiment" Keys fed his conscientious-objectors more calories than suggested above, comprised of "real food" which was available to the poor and to famine-victims in wartime Europe. He made them hike, too -- not heavy workouts, but far from sedentary. After a little time passed, his victims became neurotic, then psychotic.
Starvation kills ... long before one dies of starvation. AND THIS IS EXACTLY WHAT MAINSTREAM DIETARY ADVICE REPLICATES.
Bodies do not function WELL on reduced-calorie diets. Their little reptilian-brain control systems think there's something wrong, and they make a host of little adjustments for the sake of survival, which effectively reduce our quality of life.
We can accustom ourselves to functioning like that, but it totally sucks. We get fatigued and stressed, our organs don't work optimally, and to combat the misery we compromise on techniques which help us to cope -- sugar, alcohol, tobacco, hedonic drugs, other kinds of "thrills." We end up with "first world problems" which our distant ancestors would have laughed at.
This is one of the benefits of being on a low-carb, real-food regimen -- eating enough minimally-fattening foods to satisfy our appetites, we tend to be able to ingest enough energy so that our bodies DON'T think we're in danger of starving. They DON'T perceive they're being operated on low-quality fodder which fill the belly without FULfilling nutritional requirements.
If we ARE running on a low-fuel light for a long time, we have to train ourselves to be able to ingest more -- if we jump right in, we'll only gain weight! I'll always remember reading about those studies which had people on ultra-low-calorie diets for extended periods of time, and when the subjects added just a couple of hundred more calories per day they actually stored it as fat. :-( Because they trained their bodies to get along with less, nine hundred calories became a weight-gain diet.
That sort of thing is why i rant against MERE calorie-restriction as a weight-loss tool. It IS possible to screw up your metabolism so badly that long rehabilitation is the only way back to health. It's also why i get so angry and disgusted with naturally-thin people who accuse the overweight of lying about their diet-and-exercise reports -- OF COURSE it's easy to underestimate in food-records, but it's also easy to "do everything right" and still show no progress ... when the advice was wrong to begin with.
I have a sneaking suspicion that all the low-meat dietary advice a strong driver of constant hunger. Wooo-like people excepted (who have physical issues with a too-high meat consumption), following advice for bare-minimum protein intake can leave some feeling ravenous. If i, as the example i know best, don't get enough meat it doesn't matter how much of other macronutrients i ingest. I. NEED. NATURAL. ANIMAL. PROTEIN. No compromise possible.
We should all stop following other people's rules of what we should eat (and how much), and do a careful experiment on ourselves. Only this provides a reliable set of instructions for our personal body-owner's manual.