If you wear a size 18in US men's shoes and lose 22 pounds, can it drop your shoe size down to a 16?
if the loss in weight is edema (fluid), then yes, your shoe size may be smaller.
Even without gross edema, I would bet that being significantly overweight would add some extra intravascular fluid volume pooling in your feet. That said, numerical shoe size reflects the length of your feet. I’d imagine fluid probably affects the width more than the length. You’d be less likely to go from size 18 to size 17, and more likely to go from, say, 18E to 18D