Why do we crave sugar?

Sugar is a quick source of glucose, the fuel our cells and especially our brains rely on, so evolution wired us to seek it out. When we eat something sweet, the brain reward circuits release dopamine, the same neurotransmitter involved in pleasure and motivation, reinforcing the behaviour. For our ancestors, sweet ripe fruit was a rare and valuable source of energy, so a strong appetite for sweetness improved survival. In the modern world, however, cheap and abundant sugar can hijack this ancient system, encouraging overconsumption. Blood-sugar swings also play a role: a sugary snack raises glucose quickly and then drops it, which can trigger renewed cravings soon after.