Both walking and gaining weight will increase the size of your feet both in width
and in length in my opinion, as does getting older (that's a fact).
My wife just set out on a solo walk, a four month, 2,650 mile walk from Mexico
to Canada on the Pacific Crest Trail. I just dropped her off at the Mexican border
on Sunday with a pack weight which will average between 25 - 30 lbs. We fully
expect her feet to increase at least a full size over the course of her journey as
I will be ordering and getting shoes to her along the way. How much, if any of
that is permanent is unknown at this point in time.