I'm 60 Years Old, 5'9 1/2, 190lbs..... BP Is 119/80....

I'm 60 years old, 5'9 1/2, 190lbs..... BP is 119/80.... My BMI is 16.6... (84.4 lean mass). Everything I've read says that BMI number is dangerous and indicates malnourishment! I exercise often, I'm quite active and feel the same as did when I was 35. In other words, great........ So, I'm confused. Is my BMI too low?... I have a great appetite and eat like horse.