most of us won’t have to worry about this but-
“A body fat percentage below 5 percent is regarded as a warning sign of poor health, even in elite athletes,” says Georgie Fear, R.D...”
https://www.yahoo.com/lifestyle/15-negative-effects-of-having-a-low-body-fat-127106249953.html
A few of those under-5%ers got drafted fairly high in the NBA last week.