Some people much smarter than myself, like Dr. Robert Lustig at UCSF, believe that sugar is the main cause for "diseases of affluence" like diabetes, heart disease, and cancer. I've been on the Paleo diet, which eschews refined sugar, for over four years. I've lost a lot of weight and feel better than I have felt in many years. I know this is just an n=1 study and doesn't vilify sugar in isolation, but I believe it played a huge role in making me healthier. Sugar is just as bad as those other drugs and maybe more so. Eating it is like shooting yourself, but with a very slow moving bullet. It'll catch up to you at some point.