Roughly 10 000 years ago, sugar was first domesticated in New Guinea. Roughly 8000 years ago, it was transplanted to India. Sometime around the seventh century, cultivation and some industrial production began in southern Europe, and the crusades subsequently acquainted more Europeans with sugar imported from Arab lands. Until the sixteenth century, sugar was often viewed by Europeans as having medicinal properties. Colonisation of the New World led to mass production and distribution of sugar as a major foodstuff^{( 1 –} Reference Galloway ^{5 )}. By 1713, a writer in a scholarly journal was extolling the health virtues of high levels of sugar consumption, including in beverages⁽ Reference Slare ^{6 )}. In 1893, Harley⁽ Reference Harley ^{7 )} conducted self-experiments and concluded that consumption of 250 g (approximately 4184 kJ or approximately 1000 kcal) of sugar greatly increased muscular work capacity. In 1899, a controlled trial involving soldiers reported that those given a ration of sugar were in better health, felt more vigorous and gained more weight (presumably judged to be a good thing at the time)^{( 8 )}. As the century turned, Gardner⁽ Reference Gardner ^{9 )} described sugar as a nutritional necessity that increased the health and vigour of populations. Yet, the positive health halo of sugar could not last. A generation later, authors of scientific papers did write about ‘The social problem growing out of the overconsumption of sugar’ and described school-based programmes to teach children to consume less sugar⁽ Reference Sollins ^{10 )}.

Sugar consumed in liquid form has come to be seen by some as especially deserving of scrutiny. In 1990, Tordoff & Alleva⁽ Reference Tordoff and Alleva ^{11 )} published seminal trial results showing that persons required to consume additional sugar in the form of a beverage gained more weight than did a control group given a non-energetic beverage. After 13 years, suspicion was increasing that metabolisable energy, perhaps especially sugar, consumed as liquids promoted less satiety, less energy compensation and more weight gain than did the same energy consumed in solid form⁽ Reference Almiron-Roig, Chen and Drewnowski ^{12 )}. The topic has become controversial to say the least⁽ Reference Slavin ^{13 )}, and there is substantial evidence that the strength of the supporting data has often been exaggerated and distorted⁽ Reference Cope and Allison ^{14 ,} Reference Kaiser, Shikany and Keating ^{15 )}.

Newspaper articles offer statements such as ‘People who drink sugary soft drinks do not appear to compensate by reducing calories somewhere else in their diets, so they tend to pack on extra pounds’⁽ Reference Hellmich ^{16 )} and ‘Study after study has shown that like experimental animals, people do not compensate for extra liquid calories by eating less food’⁽ Reference Brody ^{17 )}. This concept that people do not adjust their energy intake (or expenditure) to compensate for energy consumed as liquids is at the heart of the matter. Yet, is it true? Although opinions on matters of energy compensation in response to various forms of sugar intake and/or liquid energy have been offered for over 70 years^{( 18 , 19 )}, convincing data on these issues have been scarce.

In this issue of the British Journal of Nutrition, Reid et al. ⁽ Reference Reid, Hammersley and Duffy ^{20 )} offer a new and valuable piece of evidence on this question. In a study of obese adult women, those consuming sugar in liquid form at a level of 1800 kJ (approximately 430 kcal) per d gained far less weight than expected and no more weight than did women in a control group drinking zero-energy beverages. The study has several strengths. It was a controlled trial that was run for long enough to observe weight changes and that was at least partially conducted in a blinded fashion. It also has several limitations, including a modest sample size, incomplete blinding and the fact that it was not strictly randomised. I will not belabour those points here as Reid and colleagues discuss them in their article. It should also be noted that the study concerns only adult women and cannot necessarily tell us about the effects in men or children.