It's because you're only on day 3 and your body and brain are screaming out for carbs. Don't feed them carbs.

For me it got somewhat better on day 5 and then much better after 2 weeks.

I'm finding that the key is being distracted by work or other kind of business so you don't have time to think about food.

I think you're suffering from addiction withdrawal like I was, which explains the grumpiness.