For me it is when I become hypo-manic, which can last for a few months, during this time I drop every bit of fat from my body and every muscle becomes visible. There is no difference in bone pressed or non-bone pressed length. I get down to about 150 pounds. But the opposite of this holds true when I become depressed, I get up to about 215 pounds but I have gotten as heavy as 280. I lose a lot of length from my non-bone pressed measurement. I lose most of my muscle tone. I wish there was a way to get slim and keep it that way.