Ezekiel 4:13

‘And Yahweh said, “Even thus will the children of Israel eat their food unclean among the nations whither I will drive them.” '

The eating of food in this way would not only indicate the coming siege, it would also act as a reminder that because of their rebelliousness His people would be driven from the land of their inheritance to live in foreign lands that were seen as unclean. This signified that they would no longer be enjoying in full God's provision for them through His covenant. While they would still be His covenant people, and be expected to live under the terms of the covenant, a major part of the privilege would have been lost. They would no longer have their own land, and their own holy city and temple, and the privilege of living fully in ritual cleanness. They would be defiled until their period of punishment was over.