The critical question, as the journalist and historian Charles C Mann has elegantly put it, "is whether (sugar) is actually an addictive substance, or if people just act like it is". This question is not easy to answer. Certainly, people and populations have acted as though sugar is addictive, but science provides no definitive evidence. Until recently, nutritionists studying sugar did so from the natural perspective of viewing it as a nutrient – a carbohydrate – and nothing more. They occasionally argued about whether or not it might play a role in diabetes or heart disease, but not about whether it triggered a response in the brain or body that made us want to consume it in excess. That was not their area of interest.

The few neurologists and psychologists interested in probing the sweet-tooth phenomenon, or why we might need to ration our sugar consumption so as not to eat too much of it, did so typically from the perspective of how these sugars compared with other drugs of abuse, in which the mechanism of addiction is now relatively well understood. Lately, this comparison has received more attention as the public-health community has looked to ration our sugar consumption as a population, and has thus considered the possibility that one way to regulate these sugars – as with cigarettes – is to establish that they are, indeed, addictive. These sugars are very probably unique in that they are both a nutrient and a psychoactive substance with some addictive characteristics.

Historians have often considered the sugar-as-a-drug metaphor to be an apt one. "That sugars, particularly highly refined sucrose, produce peculiar physiological effects is well known," wrote Sidney Mintz, whose 1985 book Sweetness and Power is one of two seminal English-language histories of sugar. But these effects are neither as visible nor as long-lasting as those of alcohol or caffeinated drinks, "the first use of which can trigger rapid changes in respiration, heartbeat, skin colour and so on".