I was diagnosed last week 27th; and I am on 2 Metformina 500mg a day; I have been so good no pasta no bread NOTHING!! just SALAD and FISH!!! and I am still the same weight ( I know Rome was not built in a day) oh and a good half hour walk every day at least Give me a couple of pounds lost!!!
I think it varies with the individual but many people report weight loss when taking metformin and adopting low/moderate carbs. I take the same dose as you and have lost 5.5 kg ( about 12lbs) in 32 days. Keep at it and I suspect you will see loss....mine started to come off in week 2. Gone from BMI overweight to (just) inside normal
cheers