"There is nothing programmed into our brains that makes us see a box of donuts and automatically want a sugary treat" Schultz told me. "But once our brains learn that a donut box contains yummy sugar and other carbohydrates it will start anticipating the sugar high. Our brains will push us towards the box. Then, if we don't eat the donut we will feel disappointed."
From page 48 of the so far very good The Power of Habit by Charles Duhigg.