Yes, this did happen to me in a way, and it was while I was on a low-dose pill like Yaz (mine was specifically on Ortho Lo).

Basically, I started getting TOM on the third week (active pills) instead of on the inactive pills like I was supposed to. My doctor told me I was still totally covered, and she was wrong. After a couple of months of that I ended up preggo! Moral of the story: If your TOM changes for any reason, use backup birth control.

My personal theory is that losing a large amount of weight (I had lost 80 pounds when this started happening) throws the body off so much that hormone levels and everything that goes with that HAS to be affected in some way. I can't say if it's related to how many carbs a person eats in a particular day/week/month or not, but again, I'll reiterate: Use backup!