Man, I really wish you would go do some big time research on the metabolism brother. Metabolic Slowdown is a FACT!!! There is no gray area there, it is illogical to think that the body does not have the ability to modify its metabolism in order to ensure its survival. Their are countless studies on this brother. There is absolutely no question that this happens.
There is a difference between Metabolic Slowdown and Metabolic Damage. Metabolic slowdown is a fact of life, it is a survival trait developed in the times when fasting was a part of life due to food not being readily available. You even mention some of the controlling hormones as factors, while denying the legitimacy of their actions. Leptin is a metabolic controlling hormone. It is stored in your fat, and increases your metabolism when it is in high concentrations. As you lose fat your release leptin, and leptin is restored through food consumption, specifically sensitive to carbohydrate intake.
When you diet in a higher deficit for a long time and are not replenishing the leptin levels your metabolism slows down. That is quite simply how it works. There is no argument to that, it is an accepted fact. That is also the reason that true refeeds should be higher in carbohydrates because carbs increase leptin far more efficiently than other nutrients. This is why a lot of really successful PMSF type stuff has an extreme carb refeed weekly after the first 2 weeks. The Carb Nite diet I keep recommending here to those of you who are trying to stick with one of these types of diets gives you the best of all of these worlds when trying to do a drastic cut like this. You get multiple protein meals a day even those small, so you are always stimulating MPS, keeping carbs extremely low during the week so fat loss is accellerated as well, and the Carb Nite itself replenishes your leptin stores so that your metabolism does not slow down.
As intelligent and well intended as you are I really wish you would truly research this one section of information you seem to be stuck on not buying into. However metabolic slowdown is proven and is factual.
Now Metabolic Damage, yeah that is one of those scary words. Basically all it is is metabolic slowdown that was taken to the extreme. However the only thing required to fix the "damage" is a gradual and systematic reintroduction of nutrients that gradually replenish the leptin stores. However it takes much longer due to the extremes they went too.
Oh, I've researched it. I respect your view on it. And I probably push back a little too hard because I feel like it is SO over played and SO misunderstood.
First, I'm not saying that a SUCCESSFUL diet won't slow your metabolism. It will. For two reasons. One is, a lighter body requires less energy to move, so it will burn less calories throughout the day than a heavier body, regardless of diet. At the same activity levels, someone at 200 pounds will burn less calories than they would at 250 pounds. So, if you successfully diet, you slow your metabolism.
Also, while on a diet, and somewhat in line with "starvation mode" - you do have hormonal changes and energy level drops, which mean you will be more likely to conserve movement, which will mean less activity, and thus fewer calories burned.
The idea that your body can somehow slow your metabolism, however, is fairly illogical. Some of the explanations out there defy the laws of thermodynamics (not saying your that over the top MrKleen73), and frankly it doesn't make sense that a body that would "worry" about starvation, would EVER become inefficient at burning calories. The simple logic for this is, why do we store fat then? Because our body is designed to be efficient and have supply of energy. Further, the logic that your metabolism adjusts would be awesome, because it would imply that I could over eat and not store fat, because my metabolism would adjust, which of course goes against the original premise of the theory - that the body is worried about starving....if you're gonna worry about starving, why would you ever speed up your metabolism, even in times of plentiful energy?
Leptin, Grehlin, etc. - I do believe these hormones play a role, but it isn't strictly a "speed of the metabolism" function. Part of fat loss is also the ability to shuttle fat in and out of cells, not be hungry, etc. - all these things are more confounding factors. T3 and rT3... not sure there is any definitive evidence of HOW MUCH this effects metabolism. I would love to learn if there is.
And of course, just because we aren't eating doesn't mean we're "starving" necessarily - as long as our fat loss doesn't outpace the ability of our body to mobilize fat stores, then we are still getting the needed calories. Obviously, the lower you get in bodyfat, the more of a concern this becomes and then, yeah, maybe starvation mode is more of a concern, which also coincides with the research I've done.
Finally, the research I've seen, I believe showed a 40% decrease in people who dieted at 50% of their caloric needs for a period. I believe something like 25% of this was accounted for just by adjusting for weight. That left 10-15% drop (which for more people is 200-400 calories) and in reality, that could possibly be due simply to reduced activity levels from dieting. And even still, 200 calories off your TDEE during a diet isn't the end of the world if you plan for it and control it.
And beyond this, I've tracked my own results after a fairly long PSMF and going by fitbit (which is normally high for its calorie estimates from what I've read) and my diet tracking, even after the PSMF - I lose weight in a fashion that is consistent with fitbit estimates (which would be based on no metabolic slow down, and if they're high I should lose weight more slowly than the estimates).
So yeah, my saying "starvation mode doesn't exist" is a little over the top. And you are right, there are a lot of factors. What I really mean to say is, it's way over played and people give it too much credit.
Again, I totally respect your review, your help is GOLD. I just bounce this stuff all around in my head and I'm just laying out why I think these things.
Cheers all y'all.
