Out of stock amount changed

hello friends

If I have set for products which reach stock 1 to go out of stock, and then I change this to stock 0, still all products with stock 1 continue out of stock, only if I enter the product page and press save it will become in status with stock ready to be purchased. Do I have to sabe product by product so that the product assumes this change on the site wide out of stock amount parameter?

Many thanks in advance

Julio