It took about a month before I was able to start losing weight after beginning metformin. I also gave up caffeine, the cream in my decaf, started walking more and continued lifting weights, and began to really watch portion size. For me, calories do matter. On the other hand, I did add more carbs than the induction level of Atkins. This is something I have to live with for the rest of my life so I'm trying to adjust my diet to something more livable than induction. I don't eat bread, potatoes, corn, sugar, etc but I do have part of an apple on occasion and I did have about 1/4 cup of sweet potato a couple of days ago.
Metformin really helps but it isn't a magic pill. It just makes all your hard work work.