She will also get a seat on the board as part of the deal, which will
grant the company the right to use her image and name on its goods and
adverts.
Ms Winfrey is buying 6.4 million shares of Weight Watchers at $6.79 apiece.
She will also receive options to buy another 5% of the firm. The firms' shares leapt 48% to $10.03 in premarket trading.
