Calories are calories, the source doesn't matter, no good science suggests fat or sugars "cause" more weight gain. Sugar may be more of a "cause" in that it's much easier to consume sugar; a sugary soda and a fatty soda aren't as easy to consume. I personally believe food corporations are partly to blame for aggressively marketing and pushing unhealthy food as healthy, inaccurate food labeling (0% trans fat doesn't mean there is no trans fat).  However we can't get a grip on this out of control practice and put massive sin taxes on chips and soda and shit.  It falls on individuals to be ultimately responsible for themselves, their health and to be informed about what they eat.