Hi,
I can't comment on the diabetes connection but I can tell you my own story re Planters faciaitus.
I am 57, about 19 stones and reasonably fit. Went out for a long walk last summer and couldn't make it home without serious limping. Next day I could hardly put my foot down. Went to doc who diagnosed planters fasciaitus (essentially damage to the big pad that runs the length on your foot) and told me "it'll get better on its own". Turned out not to be true and a few months later I started making enquiries on the internet on a forum like this.
Advice was to stretch it every morning and run it over a tennis ball, and to go to boots and buy an orthopedic insole (around £25). Cutting a long story short, it started getting better almost immediately and its now fully recovered, although it took about six months.
The moral, as with a lot of this forum is, listen to your doc but also inform yourself as best you can.
As far as I'm aware, totally unrelated to diabetes but definitely related to being overweight.
This may or may not be connected to this post. If you want to know more, just Google "planters faciaitus" and you'll get lots of hits.