Advanced calorie deficits (Fair Warning - long post)

this really is for the more advanced or "sciency" person, I wasn't joking. This post is for those who understand the human metabolic system and are willing to read deeper.

Assumptions (terms I expect you to know, they may or may not be in this post, but they should be known to understand everything)

TDEE
BMR (the real definition)
Metabolic Rate
Adaptive Thermogenesis
Catabolism
Anabolism
Glycogen
Lipogenesis/Lipolysis
Metabolic homoeostasis
ATP (Adenosine TriPhosphate)
Mitochondria (and their function)


So we all know the well used term "calories in vs. calories out" right? For the most part, it's relatively accurate. It's the basis for most weight loss and more importantly fat loss. Defined in a more scientific manner it's the point where calories consumed is lower than TDEE. Sounds simple and easy right? Just eat less than you burn in a day and you lose weight. One Hundred percent accurate. This is a statement of fact, cannot change, there's no argument, you can't make one. It just works.
So why all the fuss? Why do people have such a hard time with weight loss if it's really that easy. Well, I'll tell you, it's because calculating TDEE is harder than you think. TDEE isn't some set number that's exactly the same every day or for every person based on some very limited number of physical facts, it's ever changing, it's different for everyone, even those who have identical statistics can be dozens or hundreds of calories different in their TDEE. Why? Genetics people, genetics.
You can copy a workout exactly, you can copy a diet plan exactly, you can have the same amount of stresses each day, you can exist in the same external temperature, sleep the same amount...etc. If you have different genetics than another person, even given all of the above, you can still fail at weight loss (or succeed) where another won't. This is why I preach knowledge of your
own body so heavily. This is why I am so adamant about tweaking your eating to fit you. Test, analyze, modify, retest, repeat until you are spot on target.
This site is great, perfect for a person to start trying to lose weight. But as we progress through the stages of weight loss, it becomes harder to estimate how many calories you need to reach metabolic homoeostasis and therefore to predict what you need to reach calorie deficit without going to far and entering into a state where the body will recognize a constant and high calorie deficit and compensate by lowering overall calorie consumption and ramping up fat storage (commonly known as starvation mode but more accurately known as adaptive thermogenesis or the famine response).

Here's some of the pieces of the puzzle that are needed to keep a consistant weight loss srategy without seriously eating into your lean mass stores or entering into that dreaded "starvation mode" mentioned above.

- The less fat you have available, the harder it is to keep a consistent deficit.
Why: Fat is NOT your body's preferred fuel. Even though fat has far more calories per gram, the type of calories are more difficult for the human body to convert to ATP. Adipose fat first needs to be liberated from the lipocytes that contain it and converted to glycerol (and some free fatty acids use directly by cells) using the process called lipolisys. Once converted, those gycerol compounds then need to be cleaved into their component glucose molecules in the liver and kidneys where they can then enter the glycolysis and gluconeogenesis pathways(the same as carbohydrates). As you can see, this is a far more expensive process calorically than the carbohydrate metabolism. It also takes far longer to acheive, which precludes fat from being the fast acting energy source humans need, especially in times of high stress (like exercise). Back to the original question, because fat isn't the primary fuel source of the human body, only a small percentage is used when the body needs energy. Like any efficiency engine, the human body refuses to use less efficient energy until absolutely necessary. It will continually draw small amounts of fat when necessary to suppliment regular caloric needs, but never (except in one specific condition we will talk about later) will it recognize fat at the primary fuel source.

- A calorie is not a calorie, thus calories in vs. calories out is only "kinda" true.
A fat calorie is more expensive to use, it also takes longer to deliver and burn and cannot be delivered in a usable form to where it is needed as quickly as a carbohydrate can. Because of everything stated above, it should be obvious now why trying to force the body to use only fat as a fuel source is a risky proposition. It's possible, but you must be perfectly balanced to do this. A much better way is to eat the correct number of calories to keep your body "thinking" it's got plenty of energy, then use exercise to elicit that deficit we all want, which forces the body to pull small amounts of fat to make up the difference while still having plenty of "fast" energy (in the form of carbohydrates) to fuel the exercise itself. Things that require a slower trickle of energy like breathing, walking, doing the dishes, sweeping the floor...etc. (very low stress activities) can be supplemented by fat. In every study done that I've ever read (and that's hundreds), fat energy isn't tapped into by the moderate to high level activity until at a minimum the 15 minute mark, and most not seeing fat reserve usage until well after 30 minutes, see my
above description of fat metabolism to understand why. For the record, protein has a similar (but slightly different) pathway to energy.

- Yes, fat and protein can be used as primary fuel sources, but it's not how your body wants it.
Ketogenesis, or more as it's more commonly known, "low carb", is essentially starving your body of fast acting fuel and forcing the citric acid (Krebs) cycle into overdrive to produce the glucose needed to keep energy levels up. Ketones are not a preferred source of fuel, they can, however, be used after a more lengthy and expensive process to be converted to fuel. Cell mitochondria use Ketones in a similar but less effective manner. The major issues with Ketogenesis are 2 fold. First is that it takes longer to convert to usable energy in the body, thus precluding many from using this method during High Intensity cardiovascular activity such as HIIT training. Second, because of the by products released, it can stress the kidneys and liver higher than normal, carbohydrate heavy metabolic pathways. While in an healthy adult this is usually not an issue, if there is a history or condition in these organs, severe problems can develop. Also to note that these activities cause water to be stored differently in cells and dehydration is a concern if water is not monitored closely. Ketogenesis is not for the faint of heart and requires a thorough knowledge of your body and a dedication most just don't have. Yes, initial weight loss in Ketogenesis is fast, but that's mostly because of the loss of up to 15 lbs of water, which is usually immediately replaced when
carbohydrates are returned to the body in any substantial and sustained amount.

- Whether you want to believe it or not, starvation mode is real
Many people may have the wrong idea of what starvation mode is, but that doesn't make it false, it makes their concept of it false. It's up to us as intelligent human beings to combat misinformation where ever we can. That means when someone spouts something wrong or silly about starvation mode. Speak up. But do it respectfully, and provide not just a response, but proof. There's plenty out there I can give you tons of studies if you need them. But just talking about the metabolic processes surrounding this state should be enough( no studies needed, these are facts about the body, not up for debate). What starvation mode isn't: it has nothing to do with 1200 calories, it doesn't happen after 1 day of not eating, and it is NOT starvation (two completely separate terms), starvation is a state, starvation mode is a process. Yes someone in prolonged, deep starvation mode can eventually starve, but except in the case of complete absence of food, starvation istself is extremely rare and someone giving you case studies on starvation to prove points on starvation mode are only showing their scientific ignorance.
Starvation mode IS, in it's simplest form, your body's metabolic processes recognizing, over the course of days or more likely weeks, that it's receiving far fewer calories than it needs. This triggers two major functions. First, when in starvation mode the body will reduce energy consumption wherever it can, starting with the least important (in it's opinion) functions first. Second the body will use any extra calories it can find and store them as fat. So when someone says starvation mode is a myth, please try to explain that it's not a myth, it's just difficult to prove, and you can't just blithely say someone's in that state without some serious analysis.

Conclusion:
All this being said, what's the point? Well the point is to get you, the informed human, thinking about more than just calories in vs. calories out. If you're struggling to lose weight. Do some really thoughtful analysis, figure out what area you're probably lacking in, tweak your routine or diet then give it TIME to let your body adjust. Then re-analyze and decide whether it's working, if not, keep tweaking. Use your knowledge. Don't become frustrated with the process, treat it like a challenge. Knowledge will eventually allow you to succeed.


Hope this is useful to someone. Feel free to comment, question, even debate.

Regards

-Steve H.