1. Lots of sugar that is added to food/beverages comes in the form of fructose, which only the liver can metabolize. When fructose enters the liver and it is already loaded with glycogen most all of this sugar is turned into fat.
2. There are zero vitamins and minerals in sugar. It contains "empty calories".
3. Some of the fructose sugar that is eaten can end up deposited in the liver and lead to non-alcoholic fatty liver disease.
4. Sugar is bad for your cholesterol and triglycerides.
5. Too much sugar in one's diet causes insulin resistance which in turn leads to obesity.
6. In addition to obesity too much sugar can also lead to diabetes and heart disease.
7. Sugar doesn't trigger proper satiety, which then contributes to a higher calorie intake.
8. Sugar is addictive.
9. Resistance to the hormone leptin can also be developed, which is a major reason why people overeat.
Personally, I'm a fan of "in all things moderation".... with the exception of moderation of course!
** Taken from 9 reasons to avoid sugar as if your life depended on it c/o Authority Nutrition.