Herbalife (HLF) shares rose in afternoon trading Thursday after the weight loss company defended itself from a recent attack by short seller Bill Ackman. The SEC opened an investigation into Ackman's claims on Wednesday. Herbalife shares rose 1.4% after CEO Michael Johnson said Herbalife was a "legitimate company" at an investors meeting in New York. Executives said 31% of orders in the U.S. last year were shipped to customers who were not