Hmmm... DD is about 40 pounds I think, 5 years old, and she weaned in December. She was 6 lbs. 6 oz. when born. So no, I think she was more than 5 x her birthweight.
I thought it made total sense though that she weaned in December and as of about February, she started grinding her teeth like mad during the night. A friend the same age was doing it too, and me and the mom were discussing it. We called the dentist to see if it was a problem. Dentist said, no, if they just started doing it, that just means they're loosening their baby teeth in preparation for them to fall out.
So DDs weaning seems to be on track with her getting of adult teeth.