Accumulating evidence points towards a role for sugar and other refined carbohydrates in the development of overweight.
Research suggests that sugar increases bodyweight mainly by promoting overconsumption of energy (although the effects of sugar on body fatness independent of changes in weight could not be assessed).
This, and other evidence, suggests that sugar intake should be limited, but questions remain.
No clear threshold exists for the many adverse effects of sugar intake; in general the association seems to be roughly linear, which make a limit somewhat arbitrary. Current intake of added sugar in the US and UK is about 15% of total energy.
Source: BMJ 2013;346:e8077