Ackman Vows to Take Bet Against Herbalife ‘to the End of the Earth’

The activist investor William A. Ackman said on Friday that he intended to take his high-stakes bet against Herbalife, the nutritional supplements company, “to the end of the earth.”

In an interview with Bloomberg Television, Mr. Ackman said that his $11 billion hedge fund Pershing Square Capital Management has lost between $400 million and $500 million on his bet. He contends that Herbalife is a pyramid scheme, a claim Herbalife denies.

As Mr. Ackman spoke, Herbalife shares rose more than 4 percent. The shares had gained 5.3 percent to $72.04 just before noon. Since Mr. Ackman first announced he had an “enormous” short position in Herbalife last year, the shares have risen by more than 100 percent.

This has been a bruising year for Mr. Ackman, who was forced to retreat from an investment in the retailer J.C. Penney after a public fight with senior executives at the company. Still, he also announced a victory in October after selling about $800 million of his stake in Canadian Pacific Railway, nearly tripling his original investment.

Mr. Ackman began “shorting” the company late last year, eventually borrowing $1 billion of Herbalife shares to sell, taking a bet that he would be able to buy Herbalife shares back later at a cheaper price.

Speaking on the sidelines of the Robin Hood Investors Conference in New York on Friday, Mr. Ackman also addressed speculation that some investors, led by William Stiritz, the chief executive of Post Holding, may be teaming up to try to take Herbalife private.

Mr. Ackman told Bloomberg that such a scenario would mean “more opportunity for us to be short the company.”

The hedge fund manager is known for taking strong views and bets on companies. In a letter to investors in October, Mr. Ackman said, “We continue to have enormous conviction in our investment thesis.” But at the same time, Mr. Ackman also told investors that he had begun to pare back his bet against Herbalife.

“This is not a trade for me. We’re going to take this, as I say, to the end of the earth,” he said on Friday.

Mr. Ackman also indicated that the fund was always looking for an idea. “If you have a good idea, send it to Pershing,” he said.