I've been noticing recently that (warning: TMI) my poop has been kind of sweet smelling, which I think is attributable to being in ketosis just as sweet smelling breath is. Then I got to thinking that breast fed babies have kind of sweet smelling poop as well. So I googled "baby sweet breath" and got millions of hits. The babies in question were breast fed when it was mentioned. Usually there was lots of advice to take the baby to the doctor right away to check for type 1 diabetes, but the babies ended up being pronounced healthy.
So, sweet smelling breath and poop? Does this mean that most or all breast fed babies are in ketosis? That would be interesting. And does that answer the question of why acetone, which isn't a sugar, smells sweet to us? I'm thinking there could be an evolutionary advantage to babies' smelling sweet to their parents.
If we ever have another baby, I'm going to use some ketostix to find out whether this is the case.