Not only are they unsubstantiated, but the U.S. government is actually suing the Bodyflex people for false advertising:
"The Federal Trade Commission has sued the marketers of the BodyFlex+ System (“BodyFlex”) for falsely advertising that BodyFlex causes fast inch loss and fat loss. The FTC’s complaint, filed in federal district court, names as defendants Savvier Inc. and Savvier LP, California companies; their principals, Jack Ching Chung Chang, Jeffrey T. Tuller, and Keith Greer; and BodyFlex “creator”and spokesperson Greer Childers."
more at this link:
http://www.ftc.gov/opa/2003/11/bodyflex.htm