"Patients with type 2 diabetes who are overweight but not obese live longer than those who are underweight or normal-weight, according to a study is published in Annals of Internal Medicine."
So don't aim for BMI 19 or 20.
BMI 24 is far better than BMI 20 -- switch to LCHF and you won't even have to bother about BMI
Obviously they have added a small note to keep the mainstream happy.
Researchers slowly are proving what we diabetics on LCHF diet have been saying since long. We don't even bother about BMI as it is a useless number, unless overly obese. It's just a cover up for a BAD diet (High Carb Low Fat) which is called "Healthy and Balanced" by the so called scientists pushing that diet for selling more drugs.