The mere sight of a slice of gooey chocolate cake, a cheesy pizza, or a sizzling burger can drive us to eat these foods. In terms of evolution we show preference for high calorie foods as they are an important source of energy. We tend to crave these rich, tasty foods not only when we are hungry, but when we are emotional, bored, or stressed out.

We show a preference for these sugary and fatty foods as they are not only energy dense, but because our brain releases certain neurotransmitters when they are eaten. These neurotransmitters include dopamine and serotonin, which are involved in pleasure and act as reward signals. So the brain reward system is “tuned in” to attend to these sugary, fatty foods, and this leads to cravings that can increase consumption.

– Amy Reichelt

via Can you train your brain to crave healthy foods?.