I attended a lecture for prof scopinaro in port saied claiming that BPD is not a weight loss surgery in those patients and it cures diabetes by unknown mechanism.
Of course a BPD/DS will cause weight loss. However in this particular situation, the aim is to improve the metabolic situation. Therefore many surgeons would prefer to call it metabolic (rather than bariatric) surgery.
Personally, I would prefer to do a sleeve gastrectomy in a type 2 diabetic patient with BMI < 30, rather than a gut mutilating BPD/DS (which in my opinion should be reserved for superobese patients).