The first that I remember hearing of low body fat being dangerous was regarding a USC Trojan running back in the 1970s named Ricky Bell.
I had a buddy who worked in the clinic that served USC’s athletic department. It had a hydrostatic dip tank that measured body fat and IIRC Bell set the record for lowest % that they had ever recorded.
Bell went on to an NFL career, but fell ill and died very young at age 29. The reports were that his illness was connected to his extremely low percentage of body fat.
Extremes of most things are bad somehow, I guess.
But extremely low body fat is not something I personally have had to worry about!
(And I understand a bit of a reserve is good when fighting certain diseases, such as cancer.)
In March 1982, McKay sent him to the San Diego Chargers, but suffering from weight loss, aching muscles, and severe skin problems, he retired before the 1983 season.[3]
Death[edit]
Bell died at age 29 of heart failure caused by the disease of dermatomyositis.[1][2][3][4] Mario Van Peebles portrayed the player in the 1991 made-for-television movie, A Triumph of the Heart: The Ricky Bell Story, which was based on the life of Ricky Bell. Bell’s remains were interred in the Inglewood Park Cemetery in Inglewood, California.
He was survived by his wife, Natalia; his 10-year-old son, Ricky, Jr., a 3-year-old daughter, Noell, and his mother, Ruth.