Those sorts of calculators should always be taken with heaps of salt because there's just no way to account for all of the potential variables between Person A and Person B. In a sense it
is true that your body "adjusts" to the calories that you eat, but only in the sense that once you've shed a certain amount of weight that you acquired from over-eating, dropping lower than that isn't going to be possible again unless you drop out even more calories, or start burning more calories through exercise.
The common misconception is that the body just "adjusts" to the food you're eating and it's suddenly become this magical machine that decided that food X is now fattening when it's the same food you've been eating to lose weight this whole time, when in actuality you were 40lbs overweight because you were eating too much, so you stopped eating as much and you dropped 20lbs. However, you're
still either eating too much or not exercising enough, and the combination of the two is enough to maintain that extra 20lbs.
The body didn't decide to just stop dropping fat, the body's just being fed what it requires to maintain that new level, and the lower you go, the more strict the 'rules' get. Going from 300lbs to 200lbs can happen in the blink of an eye. 200 to 190 will take a decent bit longer. 190 to 180 will take almost as long as the two combined, etc. The lower that you get your body fat percentage, the harder it is to keep yourself down there. There's a reason that competitive bodybuilders don't maintain that 1%-3% body fat all year:
It's a pain in the ass.
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