HC Reform Update by Mark Sanna: The F.D.A. on Thursday is considering the first in a new generation of proposed diet pills. Analysts say Qnexa, from Vivus, is the front-runner in the $100 billion obesity market, if only because it is first to the F.D.A. Two other companies are in line for F.D.A. diet pill reviews later this year. But the field is fraught with safety issues.