Insulin Sensitivity is high from working out, so the need for a GDA then would be minimal. Weight training is the best GDA you can have. You will also want to avoid berberine around training. Berberine activates AMPK, which reduces protein synthesis/muscle growth. You can take GDA's and they do help with muscle growth by increasing glycogen uptake into muscle tissues. I would suggest spacing the dosing as far away from your workout as possible.
I remember Cooper posted this a while back:
It was demonstrated in normal mice too, but I think the key here is understanding the big picture. Yes, berberine potently induces AMPK, but in trained individuals, this will simply increase glucose flux (and subsequent glycogen storage) in muscle tissue.
There was a study but these were on obese people (Over BMI of 30) so take it with a grain of salt, Most of us on here are not in that category, and this had no exercise included in the study (most of us weight train or do forms of cardio)
https://www.ncbi.nlm.nih.gov/pubmed/22739410
using 1500mg/day berberine for 12 weeks showed moderate benefits in weight/fat loss, and no change in non-fat mass (exercise was not part of the study protocol; subjects kept their current habits, and no altered exercise habits were observed).