It varies by sport. Endurance athletes: 5-12% (men), 12-20% (women). Team sport athletes: 8-15% (men), 15-25% (women). Strength athletes: 10-20% (men), 18-28% (women). Performance, not a specific number, should guide body fat goals.

Yes. Too-low body fat can impair endurance, recovery, hormonal function, and immune health. Female athletes below 15% and male athletes below 5% risk Relative Energy Deficiency in Sport (RED-S), which can cause injuries, illness, and decreased performance.

The Navy method provides a reasonable estimate for tracking trends, but athletes seeking precise measurements should use DEXA scans, hydrostatic weighing, or Bod Pod testing. The Navy method can underestimate fat in very lean athletes and overestimate in very muscular ones.