[Bognar]

That image looks like unscientific nonsense. Craving sugar means I need carbon? Carbon is the building block of every organic chemical, and elemental carbon has very little use in the body. It's near meaningless to say you need carbon.

The answer is fortunately simpler, craving sugar probably means your blood sugar is low, or that it crashed after a spike. Counterintuitively, people can avoid this by eating things with less sugar overall or with complex sugars. Requiring the body to break complex sugars down into simple sugars takes time, which keeps your blood sugar from spiking too high.