Eh, there probably will be.  There isn't any way to manufacture calories out of nothing but there are plenty of ways to stop calories from being properly absorbed. This is why "unexplained weight loss" is a common symptom of serious illness.  In addition, there is an insane amount of money to be made in a true fat pill. Rest assured though, they'll find some way to be "fat".  It will still be obvious who the fatties are.