The Herbalife logo is seen on a building housing some of their offices in downtown Los Angeles, California April 28, 2013. Herbalife will report their earnings on April 29. REUTERS/Lucy Nicholson

NEW YORK (Reuters) - Herbalife Ltd. HLF.N commissioned a secret report to understand what made activist investor William Ackman tick as he accused the company of being a fraud and bet its share price would collapse to zero, a new book shows.

Nearly two years after Ackman first began researching his $1 billion short-bet against Herbalife, the nutrition company paid $100,000 in 2014 for a 30-page dossier to help management understand and then react to its adversary, television journalist Scott Wapner wrote.

Ackman alleged in public presentations that the company was running an illegal pyramid scheme where members were paid more to recruit new people than for selling the actual product and said many times that the stock price would tumble to zero once the government investigated. Herbalife denied the allegations and its share price traded at $102.37 on Tuesday.

Wapner’s book “When the Wolves Bite; Two Billionaires, One Company, and an Epic Wall Street Battle” is being published on Tuesday. The existence of the dossier had not been previously reported. Herbalife did not respond to a request for comment and a spokesman for Ackman declined to comment.

Ackman is described in the dossier as being “fiercely competitive,” “extremely smart,” and “aggressive and competitive in all things,” Wapner writes, quoting the report. Ackman “believes he is in the right and stubbornly, inflexibly, sticks to his positions,” Wapner adds, quoting the report.

The battle over Herbalife’s future pitted Ackman, who runs $8.2 billion Pershing Square Capital Management, against Wall Street rivals including Carl Icahn, who bought a big stake in the company in 2013, making it one of Wall Street’s most expensive and enduring fights.

Forensic psychiatrist Park Dietz relied on media reports and television clips to compile the dossier and did not interview his subject directly, Wapner wrote.

Ackman exited the Herbalife short bet this year, ending his six-year long mission. While Ackman lost money on the bet, the Federal Trade Commission investigated Herbalife and settled with the company in July 2016. Herbalife paid $200 million to compensate consumers who had been deceived into believing they could earn “substantial money” by selling Herbalife products, and the company was forced by the FTC to restructure its business.