Why do I feel so hungry and shaky on the first day of my diet?

Normally I eat a lot of carbs including some Bad carbs like white bread... Well I started a diet.. had a salad when I woke up, then started feeling shaky and weird a couple hours later.. so I had a slice of whole wheat bread with almond butter, a kiwi, 2 baby carrots, and a mini cucumber.. then I had homemade vegetable and lentil soup. But all day I felt so hungrey and shaky.. is my body just like in shock from no carbs or what? I have been moving around all day too.