How much body weight is below 10% body fat?

Probably TOO LOW. If your weight is 150# & 15# is fat, then 10% body fat classification women (% fat) men (% fat) essential fat 10-12% 2-4% athletes 14-20% 6-13% fitness 21-24% 14-17% acceptable 25-31% 18-25% obese 32%+ 25%+.