We managed to reduce...
Not quite reduce. We managed to develop certain approximations which, albeit crude, work sufficiently well for some purposes. Of course, not all purposes.
I seem to recall that BMI and/or WHR tend to be excellent predictors of physical health.
I seem to recall they tend not. In particular, BMI is a flawed indicator as it has a pronounced bias for short and tall people.
these predictions can further be improved
Which "these predictions" -- what are you forecasting?
In particular, BMI is a flawed indicator as it has a pronounced bias for short and tall people.
And muscular people. What's wrong with WHR?
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