Thought this was mindblowing. A lot of it was familiar to me (e.g. women need a certain level of body fat) and some of it I knew as urban legend (e.g. body fat set point theory).
However, he references studies and talks about things men might experience at 5% body fat that I never expected, like extremely low testosterone.
Many men who claim to be 3 to 5% body fat are really more like 10 to 12%. 5% territory is just not sustainable - men who really go down to those levels do so briefly for bodybuilding shows.