"Starvation mode", exercise calories, dillema?

This will be long. Fair warning.
And pardon my grammar, I'm notoriously bad at grammar and spelling (I did my best, but I fear it will lack a bit in that regard).

So many people on here fight about exercise calories and the "starvation mode myth". It's infuriating. I've written this in hopes that is answers the quesitons people have about starvation mode (or underfeeding, or the famine response, or a host of other terms).
First lets get this out of the way, through years of research I've come to the conclusion that starvation mode is NOT a myth. If you understand the human body, metabolism, and how we process food and use energy, you would also realize this. These aren't opinions to be formed, these are basic biological facts that have been tested significantly and proven to be true. So please don't say "it doesn't work that way for me." That's a lie and you know it. It's more like "I didn't take the time to recognize what the right amount of calories are for me, so trying to eat less (or more) didn't work."
OK that being said. Lets launch into a quick overview of what your body needs. How adipose fat (body fat) is metabolized, and the timelines involved.
So your body requires a certain amount of calories just to function, this is called your Basal Metabolic Rate (BMR) and consists of energy needs for autonomic functions such as respiration, involuntary muscle contraction (like digestion and heart function), Central Nervous System activity...etc. Things you have little or no control over. These activities require about 60 to 75% of most people's calories. No matter what you do, you need this many calories to function, this is not a debate. The rest is all subject to variation, thermogenesis (the conversion of calories to heat), daily activity, and extra activities (exercises not occuring through normal daily activity) all add to the above total giving you your Total Daily Energy Expendature (TDEE).
Luckily for most people, they have a significant amount of calories stored in their body. Not only as fat, but also as protein and glycogen (and cholesterol to a smaller degree). Even fit and healthy folks with low body fat percent have a large amount of stored calories.
So what happens when you eat below what you need? Well, that's a complicated question, please read carefully as it comes in 3 parts. Please note, the amount of the deficit, the amount of available stored energy (see above), and the activity during the period all effect the time table below (which is why I won't specifically date any part, I'll only give estimates)

Part 1 of underfeeding is immediate (the first day or two)
Depending on the amount of deficit, the first day or two of underfeeding or complete abstinance is no "big deal" to the body. It changes a few hormones slightly in order to start pulling more fuel, but the body doesn't do much with this, it puts a little more energy into the blood stream, but in general it does what it always did, it feeds your muscles by releasing glycogen into the blood, which is taken up by muscle cells and either stored there for use (a small amount of glycogen is stored in many muscle sites, providing fast energy) or used immediately. The only difference between underfeeding and normal feeding in this sense is that the liver (which produces glycogen from glucose and mainly carbohydrates) doesn't replenish the waiting supply of glycogen as fast. Because while it CAN make glycogen from FFA's (fat) and Proteins, it's a longer, slower, and less efficient process than converting simple sugars (carbohydrates). So for this first stage, you are depleting the "ready" reserves, if you go back to normal feeding after this, nothing would change. If the deficit is small enough, the body won't change the other hormones that effect fat storage and muscle growth, The body will continue to suppliment energy production by pulling small amounts of fat to be converted. This is an optimal weight loss strategy as you maintain muscle mass in the process. And the reason why we say to stay within the right deficit range for your body fat % (ultimately, this is where the starvation mode argument begins). Regardless, no significant hormonal changes occur in the first stage.

Part 2 hormonal changes occur in underfeeding
This is the part where glycogen stores are reaching dangerously low levels. This affects all aspects of the body, although the change is not immediately noticable, it does happen. Measureable decreases occur in concentration levels and muscular endurance can occur. Hormonally, our body increases leptin levels quicker and reduce ghrelin levels. Leptin is the hormone that makes you "feel full" and ghrelin is the hormone that makes you feel hungry. Thus you don't feel as hungry. This is a survival mechanism for the body, someone focused on hunger isn't as effective at other aspects of life.
At this point, given a large enough deficit to trigger these changes, your body emphasizes 2 things, 1) the citric acid cycle (conversion of proteins and fats to energy) becomes more prevelant. 2) Least used muscles begin canablization.
This means weight loss, but not necessarily good weight loss. Also, hydration becomes more of an issue as ketosis reduces water intracellularly, which means less available water. Which contributes more to weight loss, but not real weight, just water weight.
You've just begun the process of burning protein, no major muscle loss happens yet, and for the next week to three weeks, assuming a large enough deficit, you don't notice it, but it's happening. Given a large enough deficit, you're doing a lot of (reversable) damage to the body now, bones are leeached to provide more calcium to counteract the high acidic byproducts of the citric acid cycle, Free radicals increase in the blood (which can cause an increase in arterial plaque), and the liver and kidneys work harder to remove the acidic nastyness produced from that same citric acid cycle. Also, the less important (by your body's ideas of importance) autonomic functions begin to slow down to reduce the energy pressure present, specifically the immune system becomes less efficient (bad news there).
Lastly, the hormones in your body that govern fat storage change. They tell the body to store more fat. The body considers fat the "last line of defense" against starvation. And it figures it's better to reduce the parts of the body that burn calories, than to deplete the stores of energy. It's simple math really, before you deplete the last of the money in your bank account, first cut out all the unnecessary spending, then what money you do have will last longer and thus give you more time to find an alternate source of income. This is the same principle with the body and fat.

Part 3 long term underfeeding
This can begin anywhere from 10 days to six weeks depending on how large the deficit is. The body is fully in "panic mode" now. Storage of fat is a primary concern to the point where now both protein and carbohydrates coming in are shunted off in large amounts to fat storage. Muscle mass is critically low or starting to become critically low. If the person is keeping track, they will now see that their stamina and power is both significantly lower. And they will have large periods of the day where they are tired and/or lethargic, and could even exhibit "colds" and acheness very easily.
This point is where the brain is criticaly effected and organs can begin slowing down their efficiency. The long term health risks are now an issue. Some organs can shut down in parts, and sometimes these parts never start back up again. Compromised thought processes can dull perception and lead to balance and awareness issues. Sleeping becomes more difficult. It's a cycle that can end in chronic diseases and sometimes even death. I don't say this to scare folks, it's just the logical outcome (although would take quite a while unless in full blown starvation).
The good news is that you can quickly recover from this state (mostly), hormonally. But the physical manifestations of it can linger for months or even years. The most insideous part of this state is that the affected person is generally unaware of their slide down. Since the brain is affected with the body, perception becomes affected and you simply don't "notice" the cause. Accute symptoms are the only way a person in this condition usually realizes the issue. That or a very perceptive spouse or friend.

NOTES from my observations:
Look, I know many of you don't "believe" in starvation mode, but I urge you to stop and think about it. Do you not believe in the well documented, scientifically prove concept? Or do you think that you just received so much conflicting and half-right information that you don't know what to believe?
Now can we please stop saying starvation mode is a myth and change it to. "You don't understand starvation mode correctly" instead? That's all I'm asking.

As to the finer points of recognizing how many calories are "enough" for you. That's easy enough to estimate (with some impressision I admit, but it'll get you in the ballpark). Just find your approximate BMR (there's a ton of sites out there that do this, go to webMD and put metabolism calculator in, you'll find their tool for TDEE) and multiply by 1.25 (in this example) and you'll get close to your TDEE
Quick facts to help you:
-The more body fat you have, the greater your deficit can be.
-The more you work your muscles when in a deficit, the lower the muscle loss will be during that deficit (we all lose muscle in deficit, but the percentage lost can be altered with work).
-Your body does NOT wait until 5% body fat to burn muscle. Not sure where that myth came from, but it's patently false.
-Low/no carb diets don't lose fat any faster than other mainstream diets, but can be effective for people with "carb addictions", metabolic diseases, or certain allergies, and if done correctly are considered safe.

Finally, can we PLEASE stop using anecdotal evidence to prove your point. Just because YOU didn't adhere to the strict set of results state above, doesn't mean they aren't true, more likely is that you had factors you either didn't account for or were in different amounts (or timelines) than you thought, thus changing the results. (For example, you miscalculate your exercise calories, or under count your calorie intake).

For further reading. I can send you links to a dozen or so research studies and/or medical books that focus on human metabolism (I may post some here, but this is already really long so if I do, it'll be in a reply if there's enough response for it). Or you can trust that I have no hidden agenda, have done the research, and am not trying to trick anyone. I have no "skin in the game", I'm just a former fat guy, who now mentors people on here when I can. You can ask thousands of members who've been on here, I've been around a long time, and have done my best to bring well thought out, researched information. Feel free to PM me if you want some links or guided information.

-Banks