Mine went from 8 1/2 Regular to 9 Narrow. Supposedly, because I became a runner, my arch dropped and elongated my foot. Also, when I was a teen and young woman, I always wore a narrow so it may be that I was destined to be a narrow at a healthy weight.
But, yes you can definitely expect shrinkage from all over your body--even your foot.
At my highest weight, I was wearing a 10W. This was mostly casual shoes - any dress shoes or shoes that are usually more narrow by nature, I couldn't wear. Not being able to find shoes to wear was one of the major instigators to me losing weight. Health, clothing, my sense of self all were as well - but shoes were one of the immediate, urgent reasons. You cannot go through life without shoes, and I was having a very hard time finding shoes I could wear.
I am THRILLED to say that 50 pounds down, I can comfortably slip my foot into most 9.5 casual shoes. Occasionally, if the make of the shoe is small, then it'll be a 10. But these are shoes I wouldn't have been able to wear before. And now I can.
I would be thrilled - and hope - that at my goal weight, I will be wearing size 8s. I'll be surprised if the jump is that great, but I remember wearing 8s when I was younger so it might be possible.
I hope so! At my lightest (14st / 196lbs) I was wearing a size 8 regular (UK). Right now I'm wearing a size 9-9.5 wide (UK). I'm hoping that by the time I reach my goal of 10st / 140lbs, I'll go down by at least another half size from where I was at my lightest (so, 7.5 reg).
It doesn't seem to take all that much - I went from a 9W to a 9 1/2 regular in the span of only 20#. I don't have the running/arch thing to fall back on ala TBG's post, but that explanation does make a lot of sense! I have noticed that with the weight loss, I'm a LOT finickier about how my clothes fit. Possibly my foot size didn't change, but I became a lot more aware of how my shoes fit too?
I've gone from a 10W and sometimes 11W to a 9 to 9.5 regular. It's kind of a drag, because the one thing I never skimped on is shoes, and I have some pretty neat shoes that are too big now.
I went from a 9WW, that's right DOUBLE wide to either a 9 regular or a 8 or 8 1/2 wide. So yes, they got smaller and way slimmer, but I wouldn't have minded even more of a loss in that area. Oh well.
Oh and even my earlobes lost weight. Really, everything shrunk. My hats became too large on me.