All I know is weaning at 6 months is ideal and 4 months + is ok if necessary.
I know before 4 months babies should have no solids.
I just have never had a clear answer why? I've heard people say it's because of allergies but I've read it has no effect, then I've heard it's due to obesity? And damaging the digestive system?
I also know someone who was on 3 meals a day at 5 weeks believe it or not!! 
And she's a perfectly healthy adult. Does this mean that the risks are kind of pot luck? That early weaning could cause problems for some but not necessary all?
Ps. This is not about wanting to wean MY child early. Just curious as I've seen conflicting information and I'm confused as to why being weaned at 5 weeks did no harm! Health visitor made out extremely early weaning would be the end of the world haha 
Thankyou! 