This is the "a calorie is a calorie is a calorie" argument, and it's not true. Sugar upsets the metabolic process in disconcerting ways, leading to fat accumulation and insulin resistance; sugar is also more addictive than cocaine[0]. Meaning that when you consume calories from sugar, you crave more sugar calories. The foods you eat do make a difference in how fat you get, because they alter your metabolism and behavior -- but Western foods are so loaded with added sugar that sugar becomes difficult to control for.