Gary Taubes has written a substantial and important book summarizing the evidence that table sugar is a toxin. In this article, from Aeon, Taubes summarizes his thoughts and marshals the evidence in a highly readable and convincing form.
Briefly, he dismisses the older idea that sugar – through its calories – causes obesity that then causes diabetes and heart disease. Instead he brilliantly summarizes the evidence that sugar – fructose in table sugar, in fact – alters metabolism so as to cause insulin resistance and obesity together.
Recently, in a far more plodding and regrettably long article I parsed through what I consider the most important evidence for what Taubes discusses: Recent trial work comparing fructose to glucose that shows the former acts like a toxin.
Read this excellent summary by Taubes, and consider buying his book – listed at the end.
Disclaimer: I do not know Taubes and have no financial connections to his book. Just admiration for a terrific public intellectual.