wouldn't have a clue how heavy Nate is but he's in mediums with the snaps done as far as they can go. I asked Kristy and she said that mediums would be good and they are. One thing though is that they are 'hipsters' not high risers. DH thought they didn't fit at first, but they do.
I got 7 - but only because I couldn't decide .....and there is far more choice for girls ones....
eta he's over 6kgs