There are several studies that suggest the gut bacteria are capable of "hijacking" our nervous system and send signals (cravings) for nutrients they need to thrive. So it's possible that the aliens living inside us want a candy bar, not us.

Our relationship with food plays a role. For example if you drink a sugar free drink, your body tastes the sweetener and brain thinks, “woo hoo sugar is coming! Let’s spend some here, here and here” starting to budget and plan efficient usage and sending/creating hormone signals accordingly in the brain. Meanwhile the accompanied sugar calories never arrive so you end up craving sweetness more as a result.