I don't believe it really affects your weight, as long as you continue to eat the same things. However, for the week I was taking it, I found it to be quite an effective appetite suppressant. I was still eating meals (including breakfast, which I'd often skip, but needed to have food to take the metformin) but I wasn't snacking at all. Once I stopped taking it, my urge for pork crunch and dark chocolate bars between meals, came back. That's probably why I haven't lost weight, since.