The amount of metformin I take is so low its very unlikely to be affecting my BGs very much at all, but it does supposedly have other indirect benefits according to my doctor, although she also says the advice seems to be changing very frequently.
She's not unduly concerned about my low carbing, but she does also think its more likely my exercise regime thats keeping my BG's, cholesterol and trigs down. i'm at 19% bodyfat now which for a 57yo male is in the "lean" bracket (i don't feel particularly lean, but I'm not overweight either).
I don't buy into conspiracy theories much either, its too **** hard to keep such things a secret.