I ran across this message thread because I was googling a similar problem. A few days ago I went shopping for shoes and since I found a pair on clearance, I took the time to measure my feet for the first time in a while. I was very surprised to learn that my feet were now almost 1 1/2 sizes different. I couldn't believe it. I had always had a slight difference (like many people do) but this was something new. In the past my left foot typically measured size 11 and my right 10 1/2 but now my left foot was 11 1/2 and my right was just a shade over 10. I measured several times and tried a different scale but the same result. I have no idea what could be causing this. I have not noticed anything unusual (e.g. swelling or pain etc.) so I am a bit perplexed.
I have no idea when the difference came about, but it's probably been at least 1-2 years since I had actually measured both feet while shopping. I should add that i am a 47 year old male so I assume its safe to rule out a growth spurt
I have been wearing the same shoes for some time so I doubt they are the cause. About the only thing I can think of is that over the last few weeks I have been walking on a treadmill several times a week (2-3 miles per session) but I can't imagine this having such a drastic effect on my foot size (esp. in such a short time).
If anyone has any ideas or has had a similar problem I would be curious to hear about it. thanks.