I remember in the 90s, during a football game they were talking about how Jerry Rice had lowered his body fat percentage. I can’t remember the exact number, but it was lower than 5%. They showed him eating a hot dog at half time. and he said he realized that body fat percentage was too low.
Under 5% could be a problem, as i mentioned.
When i was 5.6% almost 40 years ago they started checking me often to make sure i didn’t go much lower. I used it a good excuse to drink beer!!