With metformin, you need to follow a low carb diet and avoid sugar (like a diabetic would) in order for it to really work. I had a hard time with the diet since I was taking it for the same reason as you- to counter the weight gain from antidepressants and I was hungry all the time. Talk to your doctor about this to see if there are any other things that can help. My pdoc didn't know you needed to follow the special diet - I had researched online and found out. He was surprised and interested to know.