150-160 is normal weight BMI for 5'9"
https://en.wikipedia.org/wiki/Welterweight
A professional welterweight boxer's weight is greater than 140 pounds (≈63 kg), but no more than 147 pounds (≈67 kg).
Weight classes in boxing do not account for height either so its inherently meaningless to use them to judge a persons healthy weight.
(post is archived)