Since Herbalife announced that it hired an investment bank and law firm, the stock has gained more than 35%. Shares are now down just 14% below where they were when Ackman outlined his bet against the company.

Some other notable hedge fund managers, including Bronte Capital's John Hempton and Robert Chapman of Chapman Capital, have said they're buying Herbalife's stock. Both hedge fund managers say they don't expect the FTC to take action against the company.

And so far, Ackman doesn't have too many others following his lead. He has made the biggest bet against Herbalife by borrowing 20 million shares to short them. That's roughly 82% of the company's 24.4 million shares currently on loan to short sellers, according to Markit's most recent data.