Research actually figured out the mechanism: https://www.google.com/…/www.medicalnew…/articles/amp/321407
We are always losing cells and building new ones. In a normal sleep-stress cycle, maybe 1% of those new cells become adipose tissue (ie - fat). But even ONE single bout of 48-hour elevated stress determined that MOST new cells became fat. If your sleep is crap and you don’t manage stress, there is no mathematical model which will get you leaner. You are replacing most cells with fat tissue. Burning more calories than you consume will merely result in rapid skeletal loss, not body composition improvement.
Again, calories-in/calories-out and “only macros count” proponents, please explain how your paradigm is going to work here to overcome the hormonal signaling.
Obviously, “work out more and eat less” isn’t going to change the fact that someone disproportionately grows almost exclusively fat cells when they replace cells. Just try to think this through for a minute. Imagine a heavily muscled and lean male athlete with great sleep and stress management. He's in an optimal position regarding cell turnover, wherein maybe 1% of new cells turn into fat. He may eat a lot of food, a sloppy diet at that, while maintaining a heavily-loaded strength practice, and he could easily get leaner. He might eat over 5,000 calories per day and only lift 4 days per week as he IMPROVES composition. 50 calories per day feed fat cells. 4,950 calories feed NOT-fat cells. Now imagine an obese female with volatile stress and mismanaged sleep, low muscle mass and aversion to heavy strength training. Even if she got her nutrition PERFECT, let's say at 1,650 calories while her daily expenditure is at or beyond 2,500 per day, she WILL get fatter. If only 51% of her new cells become fat cells, she'll get fatter. But with incredibly mismanaged sleep and chronic stress, and the lack of strength training, this could be as high as 90%. Maybe it is. Maybe it's 95%. Imagine it is. How in the hell is she every going to lose weight? The more calories she "burns" (this includes the production of new cells, genius) the fatter she'll get. Either way you look at it, either 842 or 2,375 calories are going to produce fat in her WHILE SHE IS IN A DEFICIT. Meanwhile only 808 or 125 calories are going to produce NOT-fat. For you advocates of calories-explain-all, show me how this math is going to work.
Moreover, the male athlete increasingly gets into a better and better position with his health and fitness prospects. Thus, from a certain point of view, his journey keeps getting easier. The woman, on the other hand, is burning up lean tissue like crazy. Every single day she loses some muscle mass and/or bone tissue (along with ligaments, tendons, cartilage, and organ reserve). This only compounds her difficulties, since less skeletal muscle equals less signaling to offset the progenitor cell percentages. To be clear, if she started at only 51% of new cells becoming fat cells, as time passes (with less lean tissue and more fat tissue) that percent will go up. Her fat gain will continue accelerating, in fact, no matter how much cardio and dieting she does.
This is again why simply referencing energy expenditure without knowledge of biology is bankrupt.
In the mice, they gained twice as much weight simply by raising glucocorticoid levels. Chronic stress must be addressed directly. We can't skirt around it with calorie theories and activity trackers.