Gymnema is supposed to help restore and raise the amount of insulin secreting cells in the pancreas which helps to enable those with poor insulin sensitivity to improve insulin output. It is also theorized it can help to lower your glycosylated hemoglobin (HbA1c), postprandial glucose levels & fasting glucose levels.
Yellow Gold (berberine) can also lower your fasted and postprandial blood glucose levels via Glut-4 translocation and also enhance insulin sensitivity. Also, berberine can help increase fat burning and reducing adipogenesis via PPARy antagonism.
It has also been said that gymnemma can help keep your sugar cravings down.
The bad part is a majority of the research down on these and other similar ingredients are all limited to rats and the few that are on humans are on either obese people or diabetic people.
Right now I use both myself along with HCA. I used to have a mix of berberine, cinnamon and Na-r-ala capped up but ran out